常见问题（二）

// 必须写的方法，和editActionsForRowAtIndexPath配对使用，里面什么不写也行- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {}

12、三个通知

NSSystemTimeZoneDidChangeNotification监听修改时间界面的两个按钮状态变化
UIApplicationSignificantTimeChangeNotification 监听用户改变时间 （只要点击自动设置按钮就会调用） NSSystemClockDidChangeNotification 监听用户修改时间（时间不同才会调用）

13、SDWebImage本地缓存有时候会害人。如果之前缓存过一张图片，即使下次服务器换了这张图片，但是图片url没换，用sdwebimage下载下来的还是以前那张,所以遇到这种问题，不要先去怼服务器，清空下缓存再试就好了。

14、上线前注意：

1）、删掉代码中所有的测试代码
2）、如果后台有审核模式，提醒后台开启此模式
3）、主流程再跑一跑
4）、全局搜索waring，检查所有标记waring的地方

15、跳进app权限设置

// 跳进app设置            if (UIApplicationOpenSettingsURLString != NULL) {                UIApplication *application = [UIApplication sharedApplication];                NSURL *URL = [NSURL URLWithString:UIApplicationOpenSettingsURLString];                if ([application respondsToSelector:@selector(openURL:options:completionHandler:)]) {                    [application openURL:URL options:@{}                       completionHandler:nil];                } else {                    [application openURL:URL];                }            }

16、给一个view截图

UIGraphicsBeginImageContextWithOptions(view.bounds.size, YES, 0.0);    [view.layer renderInContext:UIGraphicsGetCurrentContext()];    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();

17、开发中如果要动态修改tableView的tableHeaderView或者tableFooterView的高度，需要给tableView重新设置，而不是直接更改高度。正确的做法是重新设置一下tableView.tableFooterView = 更改过高度的view。为什么？其实在iOS8以上直接改高度是没有问题的，在iOS8中出现了contentSize不准确的问题，这是解决办法。

18、注意对象为nil的时候，调用此对象分类的方法不会执行

19、collectionView的内容小于其宽高的时候是不能滚动的，设置可以滚动：

collectionView.alwaysBounceHorizontal = YES;collectionView.alwaysBounceVertical = YES;

20、设置navigationBar上的title颜色和大小

    [self.navigationController.navigationBar setTitleTextAttributes:@{NSForegroundColorAttributeName : [UIColor youColor], NSFontAttributeName : [UIFont systemFontOfSize:15]}]

21、颜色转图片

+ (UIImage *)cl_imageWithColor:(UIColor *)color {  CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);  UIGraphicsBeginImageContext(rect.size);  CGContextRef context = UIGraphicsGetCurrentContext();  CGContextSetFillColorWithColor(context, [color CGColor]);  CGContextFillRect(context, rect);  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();  UIGraphicsEndImageContext();  return image;}

22、view设置圆角

#define ViewBorderRadius(View, Radius, Width, Color)\\[View.layer setCornerRadius:(Radius)];\[View.layer setMasksToBounds:YES];\[View.layer setBorderWidth:(Width)];\[View.layer setBorderColor:[Color CGColor]] // view圆角

23、强／弱引用

#define WeakSelf(type)  __weak typeof(type) weak##type = type; // weak#define StrongSelf(type)  __strong typeof(type) type = weak##type; // strong

24、由角度转换弧度

#define DegreesToRadian(x) (M_PI * (x) / 180.0)

25、由弧度转换角度

#define RadianToDegrees(radian) (radian*180.0)/(M_PI)

26、获取图片资源

#define GetImage(imageName) [UIImage imageNamed:[NSString stringWithFormat:@"%@",imageName]]

27、获取temp

#define PathTemp NSTemporaryDirectory()

28、获取沙盒 Document

#define PathDocument [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject]

29、获取沙盒 Cache

#define PathCache [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject]

30、GCD代码只执行一次

#define kDISPATCH_ONCE_BLOCK(onceBlock) static dispatch_once_t onceToken; dispatch_once(&onceToken, onceBlock);

31、自定义NSLog

#ifdef DEBUG#define NSLog(fmt, ...) NSLog((@"%s [Line %d] " fmt), __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__)#else#define NSLog(...)#endif

32、Font

#define FontL(s)             [UIFont systemFontOfSize:s weight:UIFontWeightLight]#define FontR(s)             [UIFont systemFontOfSize:s weight:UIFontWeightRegular]#define FontB(s)             [UIFont systemFontOfSize:s weight:UIFontWeightBold]#define FontT(s)             [UIFont systemFontOfSize:s weight:UIFontWeightThin]#define Font(s)              FontL(s)

33、FORMAT

#define FORMAT(f, ...)      [NSString stringWithFormat:f, ## __VA_ARGS__]

34、在主线程上运行

#define kDISPATCH_MAIN_THREAD(mainQueueBlock) dispatch_async(dispatch_get_main_queue(), mainQueueBlock);

35、开启异步线程

#define kDISPATCH_GLOBAL_QUEUE_DEFAULT(globalQueueBlock) dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), globalQueueBlocl);

36、通知

#define NOTIF_ADD(n, f)     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(f) name:n object:nil]#define NOTIF_POST(n, o)    [[NSNotificationCenter defaultCenter] postNotificationName:n object:o]#define NOTIF_REMV()        [[NSNotificationCenter defaultCenter] removeObserver:self]

37、随机颜色

+ (UIColor *)RandomColor {    NSInteger aRedValue = arc4random() % 255;    NSInteger aGreenValue = arc4random() % 255;    NSInteger aBlueValue = arc4random() % 255;    UIColor *randColor = [UIColor colorWithRed:aRedValue / 255.0f green:aGreenValue / 255.0f blue:aBlueValue / 255.0f alpha:1.0f];    return randColor;}

38、获取window

+(UIWindow*)getWindow {    UIWindow* win = nil; //[UIApplication sharedApplication].keyWindow;    for (id item in [UIApplication sharedApplication].windows) {        if ([item class] == [UIWindow class]) {            if (!((UIWindow*)item).hidden) {                win = item;                break;            }        }    }    return win;}

39、修改textField的placeholder的字体颜色、大小

[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];[textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"];

40、统一收起键盘

[[[UIApplication sharedApplication] keyWindow] endEditing:YES];

41、控制屏幕旋转，在控制器中写

/** 是否支持自动转屏 */- (BOOL)shouldAutorotate {    return YES;}/** 支持哪些屏幕方向 */- (UIInterfaceOrientationMask)supportedInterfaceOrientations {    return UIInterfaceOrientationMaskLandscapeLeft | UIInterfaceOrientationMaskLandscapeRight;}/** 默认的屏幕方向（当前ViewController必须是通过模态出来的UIViewController（模态带导航的无效）方式展现出来的，才会调用这个方法） */- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation {    return UIInterfaceOrientationLandscapeLeft | UIInterfaceOrientationLandscapeRight;}

42、获取app缓存大小

- (CGFloat)getCachSize {    NSUInteger imageCacheSize = [[SDImageCache sharedImageCache] getSize];    //获取自定义缓存大小    //用枚举器遍历 一个文件夹的内容    //1.获取 文件夹枚举器    NSString *myCachePath = [NSHomeDirectory() stringByAppendingPathComponent:@"Library/Caches"];    NSDirectoryEnumerator *enumerator = [[NSFileManager defaultManager] enumeratorAtPath:myCachePath];    __block NSUInteger count = 0;    //2.遍历    for (NSString *fileName in enumerator) {        NSString *path = [myCachePath stringByAppendingPathComponent:fileName];        NSDictionary *fileDict = [[NSFileManager defaultManager] attributesOfItemAtPath:path error:nil];        count += fileDict.fileSize;//自定义所有缓存大小    }    // 得到是字节  转化为M    CGFloat totalSize = ((CGFloat)imageCacheSize+count)/1024/1024;    return totalSize;}

43、清理app缓存

- (void)handleClearView {    //删除两部分    //1.删除 sd 图片缓存    //先清除内存中的图片缓存    [[SDImageCache sharedImageCache] clearMemory];    //清除磁盘的缓存    [[SDImageCache sharedImageCache] clearDisk];    //2.删除自己缓存    NSString *myCachePath = [NSHomeDirectory() stringByAppendingPathComponent:@"Library/Caches"];    [[NSFileManager defaultManager] removeItemAtPath:myCachePath error:nil];}

44、模型转字典

static NSSet *classes;- (NSMutableDictionary *)getParameterDictionary {    NSMutableDictionary *dict = [NSMutableDictionary dictionary];    Class c = self.class;    while (c) {        unsigned count;        objc_property_t *properties = class_copyPropertyList([c class], &count);        for (int i = 0; i < count; i++) {            NSString *key = [NSString stringWithUTF8String:property_getName(properties[i])];            dict[key] = [self valueForKey:key];        }        free(properties);        // 获得父类        c = class_getSuperclass(c);        if ([self isClassFromFoundation:c]) break;    }    return dict;}- (BOOL)isClassFromFoundation:(Class)c{    if (c == [NSObject class] || c == [NSManagedObject class]) return YES;    __block BOOL result = NO;    [[self foundationClasses] enumerateObjectsUsingBlock:^(Class foundationClass, BOOL *stop) {        if ([c isSubclassOfClass:foundationClass]) {            result = YES;            *stop = YES;        }    }];    return result;}- (NSSet *)foundationClasses{    if (classes == nil) {        // 集合中没有NSObject，因为几乎所有的类都是继承自NSObject，具体是不是NSObject需要特殊判断        classes = [NSSet setWithObjects:                              [NSURL class],                              [NSDate class],                              [NSValue class],                              [NSData class],                              [NSError class],                              [NSArray class],                              [NSDictionary class],                              [NSString class],                              [NSAttributedString class], nil];    }    return classes;}

45、交换两个方法实现

Class aClass = [self class];         SEL originalSelector = @selector(viewWillAppear:);         SEL swizzledSelector = @selector(xxx_viewWillAppear:);         Method originalMethod = class_getInstanceMethod(aClass, originalSelector);         Method swizzledMethod = class_getInstanceMethod(aClass, swizzledSelector);         BOOL didAddMethod =             class_addMethod(aClass,                 originalSelector,                 method_getImplementation(swizzledMethod),                 method_getTypeEncoding(swizzledMethod));         if (didAddMethod) {             class_replaceMethod(aClass,                 swizzledSelector,                 method_getImplementation(originalMethod),                 method_getTypeEncoding(originalMethod));         } else {             method_exchangeImplementations(originalMethod, swizzledMethod);         }

46、打印百分号和引号

    NSLog(@"%%");    NSLog(@"\"");

47、几个常用权限判断

    if ([CLLocationManager authorizationStatus] ==kCLAuthorizationStatusDenied) {        NSLog(@"没有定位权限");    }    AVAuthorizationStatus statusVideo = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];    if (statusVideo == AVAuthorizationStatusDenied) {        NSLog(@"没有摄像头权限");    }    //是否有麦克风权限    AVAuthorizationStatus statusAudio = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeAudio];    if (statusAudio == AVAuthorizationStatusDenied) {        NSLog(@"没有录音权限");    }    [PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {        if (status == PHAuthorizationStatusDenied) {            NSLog(@"没有相册权限");        }    }];

48、获取手机型号

    + (NSString *)getDeviceInfo {    struct utsname systemInfo;    uname(&systemInfo);    NSString *platform = [NSString stringWithCString:systemInfo.machine encoding:NSASCIIStringEncoding];    if ([platform isEqualToString:@"iPhone1,1"]) return @"iPhone 2G";    if ([platform isEqualToString:@"iPhone1,2"]) return @"iPhone 3G";    if ([platform isEqualToString:@"iPhone2,1"]) return @"iPhone 3GS";    if ([platform isEqualToString:@"iPhone3,1"]) return @"iPhone 4";    if ([platform isEqualToString:@"iPhone3,2"]) return @"iPhone 4";    if ([platform isEqualToString:@"iPhone3,3"]) return @"iPhone 4";    if ([platform isEqualToString:@"iPhone4,1"]) return @"iPhone 4S";    if ([platform isEqualToString:@"iPhone5,1"]) return @"iPhone 5";    if ([platform isEqualToString:@"iPhone5,2"]) return @"iPhone 5";    if ([platform isEqualToString:@"iPhone5,3"]) return @"iPhone 5c";    if ([platform isEqualToString:@"iPhone5,4"]) return @"iPhone 5c";    if ([platform isEqualToString:@"iPhone6,1"]) return @"iPhone 5s";    if ([platform isEqualToString:@"iPhone6,2"]) return @"iPhone 5s";    if ([platform isEqualToString:@"iPhone7,1"]) return @"iPhone 6 Plus";    if ([platform isEqualToString:@"iPhone7,2"]) return @"iPhone 6";    if ([platform isEqualToString:@"iPhone8,1"]) return @"iPhone 6s";    if ([platform isEqualToString:@"iPhone8,2"]) return @"iPhone 6s Plus";    // 日行两款手机型号均为日本独占，可能使用索尼FeliCa支付方案而不是苹果支付    if ([platform isEqualToString:@"iPhone9,1"])    return @"国行、日版、港行iPhone 7";    if ([platform isEqualToString:@"iPhone9,2"])    return @"港行、国行iPhone 7 Plus";    if ([platform isEqualToString:@"iPhone9,3"])    return @"美版、台版iPhone 7";    if ([platform isEqualToString:@"iPhone9,4"])    return @"美版、台版iPhone 7 Plus";    if ([platform isEqualToString:@"iPhone8,4"]) return @"iPhone SE";    if ([platform isEqualToString:@"iPod1,1"]) return @"iPod Touch 1G";    if ([platform isEqualToString:@"iPod2,1"]) return @"iPod Touch 2G";    if ([platform isEqualToString:@"iPod3,1"]) return @"iPod Touch 3G";    if ([platform isEqualToString:@"iPod4,1"]) return @"iPod Touch 4G";    if ([platform isEqualToString:@"iPod5,1"]) return @"iPod Touch 5G";    if ([platform isEqualToString:@"iPad1,1"]) return @"iPad 1G";    if ([platform isEqualToString:@"iPad2,1"]) return @"iPad 2";    if ([platform isEqualToString:@"iPad2,2"]) return @"iPad 2";    if ([platform isEqualToString:@"iPad2,3"]) return @"iPad 2";    if ([platform isEqualToString:@"iPad2,4"]) return @"iPad 2";    if ([platform isEqualToString:@"iPad2,5"]) return @"iPad Mini 1G";    if ([platform isEqualToString:@"iPad2,6"]) return @"iPad Mini 1G";    if ([platform isEqualToString:@"iPad2,7"]) return @"iPad Mini 1G";    if ([platform isEqualToString:@"iPad3,1"]) return @"iPad 3";    if ([platform isEqualToString:@"iPad3,2"]) return @"iPad 3";    if ([platform isEqualToString:@"iPad3,3"]) return @"iPad 3";    if ([platform isEqualToString:@"iPad3,4"]) return @"iPad 4";    if ([platform isEqualToString:@"iPad3,5"]) return @"iPad 4";    if ([platform isEqualToString:@"iPad3,6"]) return @"iPad 4";    if ([platform isEqualToString:@"iPad4,1"]) return @"iPad Air";    if ([platform isEqualToString:@"iPad4,2"]) return @"iPad Air";    if ([platform isEqualToString:@"iPad4,3"]) return @"iPad Air";    if ([platform isEqualToString:@"iPad4,4"]) return @"iPad Mini 2G";    if ([platform isEqualToString:@"iPad4,5"]) return @"iPad Mini 2G";    if ([platform isEqualToString:@"iPad4,6"]) return @"iPad Mini 2G";    if ([platform isEqualToString:@"i386"]) return @"iPhone Simulator";    if ([platform isEqualToString:@"x86_64"]) return @"iPhone Simulator";    return platform;}

49、长按复制功能

- (void)viewDidLoad{    [self.view addGestureRecognizer:[[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(pasteBoard:)]];}- (void)pasteBoard:(UILongPressGestureRecognizer *)longPress {    if (longPress.state == UIGestureRecognizerStateBegan) {        UIPasteboard *pasteboard = [UIPasteboard generalPasteboard];        pasteboard.string = @"需要复制的文本";    }}

50、cocoapods升级

在终端执行 sudo gem install -n / usr / local / bin cocoapods --pre

51、设置启动页后，依然显示之前的

删除app，手机重启，重新安装

52、判断图片类型

//通过图片Data数据第一个字节 来获取图片扩展名- (NSString *)contentTypeForImageData:(NSData *)data{    uint8_t c;    [data getBytes:&c length:1];    switch (c)    {        case 0xFF:            return @"jpeg";        case 0x89:            return @"png";        case 0x47:            return @"gif";        case 0x49:        case 0x4D:            return @"tiff";        case 0x52:        if ([data length] < 12) {            return nil;        }        NSString *testString = [[NSString alloc] initWithData:[data subdataWithRange:NSMakeRange(0, 12)] encoding:NSASCIIStringEncoding];        if ([testString hasPrefix:@"RIFF"]            && [testString hasSuffix:@"WEBP"])        {            return @"webp";        }        return nil;    }    return nil;}

53、获取手机和app信息

NSDictionary *infoDictionary = [[NSBundle mainBundle] infoDictionary];   CFShow(infoDictionary);  // app名称   NSString *app_Name = [infoDictionary objectForKey:@"CFBundleDisplayName"];   // app版本   NSString *app_Version = [infoDictionary objectForKey:@"CFBundleShortVersionString"];   // app build版本   NSString *app_build = [infoDictionary objectForKey:@"CFBundleVersion"];      //手机序列号      NSString* identifierNumber = [[UIDevice currentDevice] uniqueIdentifier];      NSLog(@"手机序列号: %@",identifierNumber);      //手机别名： 用户定义的名称      NSString* userPhoneName = [[UIDevice currentDevice] name];      NSLog(@"手机别名: %@", userPhoneName);      //设备名称      NSString* deviceName = [[UIDevice currentDevice] systemName];      NSLog(@"设备名称: %@",deviceName );      //手机系统版本      NSString* phoneVersion = [[UIDevice currentDevice] systemVersion];      NSLog(@"手机系统版本: %@", phoneVersion);      //手机型号      NSString* phoneModel = [[UIDevice currentDevice] model];      NSLog(@"手机型号: %@",phoneModel );      //地方型号  （国际化区域名称）      NSString* localPhoneModel = [[UIDevice currentDevice] localizedModel];      NSLog(@"国际化区域名称: %@",localPhoneModel );      NSDictionary *infoDictionary = [[NSBundle mainBundle] infoDictionary];      // 当前应用名称      NSString *appCurName = [infoDictionary objectForKey:@"CFBundleDisplayName"];      NSLog(@"当前应用名称：%@",appCurName);      // 当前应用软件版本  比如：1.0.1      NSString *appCurVersion = [infoDictionary objectForKey:@"CFBundleShortVersionString"];      NSLog(@"当前应用软件版本:%@",appCurVersion);      // 当前应用版本号码   int类型      NSString *appCurVersionNum = [infoDictionary objectForKey:@"CFBundleVersion"];      NSLog(@"当前应用版本号码：%@",appCurVersionNum);

54、获取一个类的所有属性

id LenderClass = objc_getClass("Lender");unsigned int outCount, i;objc_property_t *properties = class_copyPropertyList(LenderClass, &outCount);for (i = 0; i < outCount; i++) {    objc_property_t property = properties[i];    fprintf(stdout, "%s %s\n", property_getName(property), property_getAttributes(property));}

55、image圆角

- (UIImage *)circleImage{    // NO代表透明    UIGraphicsBeginImageContextWithOptions(self.size, NO, 1);    // 获得上下文    CGContextRef ctx = UIGraphicsGetCurrentContext();    // 添加一个圆    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);    // 方形变圆形    CGContextAddEllipseInRect(ctx, rect);    // 裁剪    CGContextClip(ctx);    // 将图片画上去    [self drawInRect:rect];    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();    return image;}

56、image拉伸

+ (UIImage *)resizableImage:(NSString *)imageName{    UIImage *image = [UIImage imageNamed:imageName];    CGFloat imageW = image.size.width;    CGFloat imageH = image.size.height;    return [image resizableImageWithCapInsets:UIEdgeInsetsMake(imageH * 0.5, imageW * 0.5, imageH * 0.5, imageW * 0.5) resizingMode:UIImageResizingModeStretch];}

57、JSON字符串转字典

+ (NSDictionary *)parseJSONStringToNSDictionary:(NSString *)JSONString {    NSData *JSONData = [JSONString dataUsingEncoding:NSUTF8StringEncoding];    NSDictionary *responseJSON = [NSJSONSerialization JSONObjectWithData:JSONData options:NSJSONReadingMutableLeaves error:nil];    return responseJSON;}

58、身份证号验证

- (BOOL)validateIdentityCard {    BOOL flag;    if (self.length <= 0) {        flag = NO;        return flag;    }    NSString *regex2 = @"^(\\d{14}|\\d{17})(\\d|[xX])$";    NSPredicate *identityCardPredicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",regex2];    return [identityCardPredicate evaluateWithObject:self];}

59、获取设备mac地址

+ (NSString *)macAddress {    int                 mib[6];    size_t              len;    char                *buf;    unsigned char       *ptr;    struct if_msghdr    *ifm;    struct sockaddr_dl  *sdl;    mib[0] = CTL_NET;    mib[1] = AF_ROUTE;    mib[2] = 0;    mib[3] = AF_LINK;    mib[4] = NET_RT_IFLIST;    if((mib[5] = if_nametoindex("en0")) == 0) {        printf("Error: if_nametoindex error\n");        return NULL;    }    if(sysctl(mib, 6, NULL, &len, NULL, 0) < 0) {        printf("Error: sysctl, take 1\n");        return NULL;    }    if((buf = malloc(len)) == NULL) {        printf("Could not allocate memory. Rrror!\n");        return NULL;    }    if(sysctl(mib, 6, buf, &len, NULL, 0) < 0) {        printf("Error: sysctl, take 2");        return NULL;    }    ifm = (struct if_msghdr *)buf;    sdl = (struct sockaddr_dl *)(ifm + 1);    ptr = (unsigned char *)LLADDR(sdl);    NSString *outstring = [NSString stringWithFormat:@"%02X:%02X:%02X:%02X:%02X:%02X",                           *ptr, *(ptr+1), *(ptr+2), *(ptr+3), *(ptr+4), *(ptr+5)];    free(buf);    return outstring;}

60、导入自定义字体库

1、找到你想用的字体的 ttf 格式，拖入工程
2、在工程的plist中增加一行数组，“Fonts provided by application”
3、为这个key添加一个item，value为你刚才导入的ttf文件名
4、直接使用即可：label.font = [UIFont fontWithName:@"你刚才导入的ttf文件名" size:20.0]；

61、拿到当前正在显示的控制器，不管是push进去的，还是present进去的都能拿到

- (UIViewController *)getVisibleViewControllerFrom:(UIViewController*)vc {    if ([vc isKindOfClass:[UINavigationController class]]) {        return [self getVisibleViewControllerFrom:[((UINavigationController*) vc) visibleViewController]];    }else if ([vc isKindOfClass:[UITabBarController class]]){        return [self getVisibleViewControllerFrom:[((UITabBarController*) vc) selectedViewController]];    } else {        if (vc.presentedViewController) {            return [self getVisibleViewControllerFrom:vc.presentedViewController];        } else {            return vc;        }    }}

62、runtime为一个类动态添加属性

// 动态添加属性的本质是: 让对象的某个属性与值产生关联        objc_setAssociatedObject(self, WZBPlaceholderViewKey, placeholderView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

63、获取runtime为一个类动态添加的属性

objc_getAssociatedObject(self, WZBPlaceholderViewKey);

64、KVO监听某个对象的属性

// 添加监听者[self addObserver:self forKeyPath:property options:NSKeyValueObservingOptionNew context:nil];// 当监听的属性值变化的时候会来到这个方法- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {    if ([keyPath isEqualToString:@"property"]) {       [self textViewTextChange];       } else {     }}

65、Reachability判断网络状态

NetworkStatus status = [[Reachability reachabilityForInternetConnection] currentReachabilityStatus];    if (status == NotReachable) {        NSLog(@"当前设备无网络");    }    if (status == ReachableViaWiFi) {        NSLog(@"当前wifi网络");    }    if (status == ReachableViaWWAN) {        NSLog(@"当前蜂窝移动网络");    }

66、AFNetworking监听网络状态

// 监听网络状况    AFNetworkReachabilityManager *mgr = [AFNetworkReachabilityManager sharedManager];    [mgr setReachabilityStatusChangeBlock:^(AFNetworkReachabilityStatus status) {        switch (status) {            case AFNetworkReachabilityStatusUnknown:                break;            case AFNetworkReachabilityStatusNotReachable: {                [SVProgressHUD showInfoWithStatus:@"当前设备无网络"];            }                break;            case AFNetworkReachabilityStatusReachableViaWiFi:                [SVProgressHUD showInfoWithStatus:@"当前Wi-Fi网络"];                break;            case AFNetworkReachabilityStatusReachableViaWWAN:                [SVProgressHUD showInfoWithStatus:@"当前蜂窝移动网络"];                break;            default:                break;        }    }];    [mgr startMonitoring];

67、透明颜色不影响子视图透明度

    [UIColor colorWithRed:<#(CGFloat)#> green:<#(CGFloat)#> blue:<#(CGFloat)#> alpha:<#(CGFloat)#>];

68、取图片某一点的颜色

    if (point.x < 0 || point.y < 0) return nil;    CGImageRef imageRef = self.CGImage;    NSUInteger width = CGImageGetWidth(imageRef);    NSUInteger height = CGImageGetHeight(imageRef);    if (point.x >= width || point.y >= height) return nil;    unsigned char *rawData = malloc(height * width * 4);    if (!rawData) return nil;    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();    NSUInteger bytesPerPixel = 4;    NSUInteger bytesPerRow = bytesPerPixel * width;    NSUInteger bitsPerComponent = 8;    CGContextRef context = CGBitmapContextCreate(rawData,                                                 width,                                                 height,                                                 bitsPerComponent,                                                 bytesPerRow,                                                 colorSpace,                                                 kCGImageAlphaPremultipliedLast                                                 | kCGBitmapByteOrder32Big);    if (!context) {        free(rawData);        return nil;    }    CGColorSpaceRelease(colorSpace);    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);    CGContextRelease(context);    int byteIndex = (bytesPerRow * point.y) + point.x * bytesPerPixel;    CGFloat red   = (rawData[byteIndex]     * 1.0) / 255.0;    CGFloat green = (rawData[byteIndex + 1] * 1.0) / 255.0;    CGFloat blue  = (rawData[byteIndex + 2] * 1.0) / 255.0;    CGFloat alpha = (rawData[byteIndex + 3] * 1.0) / 255.0;    UIColor *result = nil;    result = [UIColor colorWithRed:red green:green blue:blue alpha:alpha];    free(rawData);    return result;

69、判断该图片是否有透明度通道

  - (BOOL)hasAlphaChannel{    CGImageAlphaInfo alpha = CGImageGetAlphaInfo(self.CGImage);    return (alpha == kCGImageAlphaFirst ||            alpha == kCGImageAlphaLast ||            alpha == kCGImageAlphaPremultipliedFirst ||            alpha == kCGImageAlphaPremultipliedLast);}

70、获得灰度图

+ (UIImage*)covertToGrayImageFromImage:(UIImage*)sourceImage{    int width = sourceImage.size.width;    int height = sourceImage.size.height;    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();    CGContextRef context = CGBitmapContextCreate (nil,width,height,8,0,colorSpace,kCGImageAlphaNone);    CGColorSpaceRelease(colorSpace);    if (context == NULL) {        return nil;    }    CGContextDrawImage(context,CGRectMake(0, 0, width, height), sourceImage.CGImage);    CGImageRef contextRef = CGBitmapContextCreateImage(context);    UIImage *grayImage = [UIImage imageWithCGImage:contextRef];    CGContextRelease(context);    CGImageRelease(contextRef);    return grayImage;}

71、根据bundle中的文件名读取图片

   + (UIImage *)imageWithFileName:(NSString *)name {    NSString *extension = @"png";    NSArray *components = [name componentsSeparatedByString:@"."];    if ([components count] >= 2) {        NSUInteger lastIndex = components.count - 1;        extension = [components objectAtIndex:lastIndex];        name = [name substringToIndex:(name.length-(extension.length+1))];    }    // 如果为Retina屏幕且存在对应图片，则返回Retina图片，否则查找普通图片    if ([UIScreen mainScreen].scale == 2.0) {        name = [name stringByAppendingString:@"@2x"];        NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:extension];        if (path != nil) {            return [UIImage imageWithContentsOfFile:path];        }    }    if ([UIScreen mainScreen].scale == 3.0) {        name = [name stringByAppendingString:@"@3x"];        NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:extension];        if (path != nil) {            return [UIImage imageWithContentsOfFile:path];        }    }    NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:extension];    if (path) {        return [UIImage imageWithContentsOfFile:path];    }    return nil;}

72、合并两个图片

+ (UIImage*)mergeImage:(UIImage*)firstImage withImage:(UIImage*)secondImage {    CGImageRef firstImageRef = firstImage.CGImage;    CGFloat firstWidth = CGImageGetWidth(firstImageRef);    CGFloat firstHeight = CGImageGetHeight(firstImageRef);    CGImageRef secondImageRef = secondImage.CGImage;    CGFloat secondWidth = CGImageGetWidth(secondImageRef);    CGFloat secondHeight = CGImageGetHeight(secondImageRef);    CGSize mergedSize = CGSizeMake(MAX(firstWidth, secondWidth), MAX(firstHeight, secondHeight));    UIGraphicsBeginImageContext(mergedSize);    [firstImage drawInRect:CGRectMake(0, 0, firstWidth, firstHeight)];    [secondImage drawInRect:CGRectMake(0, 0, secondWidth, secondHeight)];    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();    return image;}

73、根据bundle中的图片名创建imageview

+ (id)imageViewWithImageNamed:(NSString*)imageName{    return [[UIImageView alloc] initWithImage:[UIImage imageNamed:imageName]];}

74、为imageView添加倒影

    CGRect frame = self.frame;    frame.origin.y += (frame.size.height + 1);    UIImageView *reflectionImageView = [[UIImageView alloc] initWithFrame:frame];    self.clipsToBounds = TRUE;    reflectionImageView.contentMode = self.contentMode;    [reflectionImageView setImage:self.image];    reflectionImageView.transform = CGAffineTransformMakeScale(1.0, -1.0);    CALayer *reflectionLayer = [reflectionImageView layer];    CAGradientLayer *gradientLayer = [CAGradientLayer layer];    gradientLayer.bounds = reflectionLayer.bounds;    gradientLayer.position = CGPointMake(reflectionLayer.bounds.size.width / 2, reflectionLayer.bounds.size.height * 0.5);    gradientLayer.colors = [NSArray arrayWithObjects:                            (id)[[UIColor clearColor] CGColor],                            (id)[[UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:0.3] CGColor], nil];    gradientLayer.startPoint = CGPointMake(0.5,0.5);    gradientLayer.endPoint = CGPointMake(0.5,1.0);    reflectionLayer.mask = gradientLayer;    [self.superview addSubview:reflectionImageView];

75、画水印

// 画水印- (void) setImage:(UIImage *)image withWaterMark:(UIImage *)mark inRect:(CGRect)rect{    if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 4.0)    {        UIGraphicsBeginImageContextWithOptions(self.frame.size, NO, 0.0);    }    //原图    [image drawInRect:self.bounds];    //水印图    [mark drawInRect:rect];    UIImage *newPic = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();    self.image = newPic;}

76、让label的文字内容显示在左上／右上／左下／右下／中心顶／中心底部

自定义UILabel// 重写label的textRectForBounds方法- (CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines {    CGRect rect = [super textRectForBounds:bounds limitedToNumberOfLines:numberOfLines];    switch (self.textAlignmentType) {        case WZBTextAlignmentTypeLeftTop: {            rect.origin = bounds.origin;        }            break;        case WZBTextAlignmentTypeRightTop: {            rect.origin = CGPointMake(CGRectGetMaxX(bounds) - rect.size.width, bounds.origin.y);        }            break;        case WZBTextAlignmentTypeLeftBottom: {            rect.origin = CGPointMake(bounds.origin.x, CGRectGetMaxY(bounds) - rect.size.height);        }            break;        case WZBTextAlignmentTypeRightBottom: {            rect.origin = CGPointMake(CGRectGetMaxX(bounds) - rect.size.width, CGRectGetMaxY(bounds) - rect.size.height);        }            break;        case WZBTextAlignmentTypeTopCenter: {            rect.origin = CGPointMake((CGRectGetWidth(bounds) - CGRectGetWidth(rect)) / 2, CGRectGetMaxY(bounds) - rect.origin.y);        }            break;        case WZBTextAlignmentTypeBottomCenter: {            rect.origin = CGPointMake((CGRectGetWidth(bounds) - CGRectGetWidth(rect)) / 2, CGRectGetMaxY(bounds) - CGRectGetMaxY(bounds) - rect.size.height);        }            break;        case WZBTextAlignmentTypeLeft: {            rect.origin = CGPointMake(0, rect.origin.y);        }            break;        case WZBTextAlignmentTypeRight: {            rect.origin = CGPointMake(rect.origin.x, 0);        }            break;        case WZBTextAlignmentTypeCenter: {            rect.origin = CGPointMake((CGRectGetWidth(bounds) - CGRectGetWidth(rect)) / 2, (CGRectGetHeight(bounds) - CGRectGetHeight(rect)) / 2);        }            break;        default:            break;    }    return rect;}- (void)drawTextInRect:(CGRect)rect {    CGRect textRect = [self textRectForBounds:rect limitedToNumberOfLines:self.numberOfLines];    [super drawTextInRect:textRect];}

77、scrollView上的输入框，键盘挡住的问题

推荐用IQKeyboardManager这个框架！手动解决如下1、监听键盘弹出／消失的通知2、在通知中加入代码：NSDictionary* info = [aNotification userInfo];CGRect keyPadFrame=[[UIApplication sharedApplication].keyWindow convertRect:[[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue] fromView:self.view];CGSize kbSize =keyPadFrame.size;CGRect activeRect=[self.view convertRect:activeField.frame fromView:activeField.superview];CGRect aRect = self.view.bounds;aRect.size.height -= (kbSize.height);CGPoint origin =  activeRect.origin;origin.y -= backScrollView.contentOffset.y;if (!CGRectContainsPoint(aRect, origin)) {    CGPoint scrollPoint = CGPointMake(0.0,CGRectGetMaxY(activeRect)-(aRect.size.height));    [backScrollView setContentOffset:scrollPoint animated:YES];}

78、frame布局的cell动态高度

这种通常在你的模型中添加一个辅助属性cellHeight，在模型中重写这个属性的get方法，根据你的布局和模型中的其他属性值计算出总高度。最后在tableView：heightForRow方法中，根据indexPath找出对应的模型，返回这个高度即可。

79、AutoLayout布局的cell动态高度

// 1、设置tableView的属性self.tableView.rowHeight = UITableViewAutomaticDimension;self.tableView.estimatedRowHeight = 44.0; // 这个属性非0，估计cell高度

// 2、至上而下设置cell的约束，注意，上下左右最好都要顶到cell的四周

cell

80、使用performSelector:调用函数，内存泄漏问题

当我们在开发中使用[obj performSelector:NSSelectorFromString(@"aMethod")];这类方法时可能会收到一个警告"performSelector may cause a leak because its selector is unknown".
是因为编译器不清楚这个对象能不能相应这个方法，如果不能，则是不安全的，而且编译器也不清楚该怎么处理这个方法的返回值！

使用以下代码调用即可：if (! obj) { return; }SEL selector = NSSelectorFromString(@"aMethod");IMP imp = [obj methodForSelector:selector];void (*func)(id, SEL) = (void *)imp;func(obj, selector);或者：SEL selector = NSSelectorFromString(@"aMethod");((void (*)(id, SEL))[obj methodForSelector:selector])(obj, selector);

81、一个字符串是否包含另一个字符串

// 方法1if ([str1 containsString:str2]) {        NSLog(@"str1包含str2");    } else {        NSLog(@"str1不包含str2");    }// 方法2if ([str1 rangeOfString: str2].location == NSNotFound) {        NSLog(@"str1不包含str2");    } else {        NSLog(@"str1包含str2");    }

82、cell去除选中效果

cell.selectionStyle = UITableViewCellSelectionStyleNone;

83、cell点按效果

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {    [tableView deselectRowAtIndexPath:indexPath animated:YES];}

84、当删除一个从xib拖出来的属性时，一定记得把xib中对应的线也删掉，不然会报类似[<ViewController 0x7fea6ed05980> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key的crash

点击这个叉号删除

85、真机测试的时候报错：Could not launch "你的 App"，process launch failed: Security

因为你的app没有上线，iOS9开始，需要手动信任Xcode生成的描述文件，打开手机设置->通用->描述文件->点击你的app的描述文件->点击信任

86、真机测试的时候报错：Could not find Developer Disk Image

这是因为你的设备系统版本大于Xcode能兼容的系统版本，比如你的设备是iOS10.3，而Xcode版本是8.2（Xcode8.2最大兼容iOS10.2），就会报这个错误。解决办法就是升级Xcode！

87、UITextView没有placeholder的问题？

网上有很多此类自定义控件，也可以参考下我写的一个UITextView分类 UITextView-WZB

88、移除字符串中的空格和换行

+ (NSString *)removeSpaceAndNewline:(NSString *)str {    NSString *temp = [str stringByReplacingOccurrencesOfString:@" " withString:@""];    temp = [temp stringByReplacingOccurrencesOfString:@"\r" withString:@""];    temp = [temp stringByReplacingOccurrencesOfString:@"\n" withString:@""];    return temp;}

89、判断字符串中是否有空格

+ (BOOL)isBlank:(NSString *)str {    NSRange _range = [str rangeOfString:@" "];    if (_range.location != NSNotFound) {        //有空格        return YES;    } else {        //没有空格        return NO;    }}

90、获取一个视频的第一帧图片

    NSURL *url = [NSURL URLWithString:filepath];    AVURLAsset *asset1 = [[AVURLAsset alloc] initWithURL:url options:nil];    AVAssetImageGenerator *generate1 = [[AVAssetImageGenerator alloc] initWithAsset:asset1];    generate1.appliesPreferredTrackTransform = YES;    NSError *err = NULL;    CMTime time = CMTimeMake(1, 2);    CGImageRef oneRef = [generate1 copyCGImageAtTime:time actualTime:NULL error:&err];    UIImage *one = [[UIImage alloc] initWithCGImage:oneRef];    return one;

91、获取视频的时长

+ (NSInteger)getVideoTimeByUrlString:(NSString *)urlString {    NSURL *videoUrl = [NSURL URLWithString:urlString];    AVURLAsset *avUrl = [AVURLAsset assetWithURL:videoUrl];    CMTime time = [avUrl duration];    int seconds = ceil(time.value/time.timescale);    return seconds;}

92、字符串是否为空

+ (BOOL)isEqualToNil:(NSString *)str {    return str.length <= 0 || [str isEqualToString:@""] || !str;}

93、将app上传到App Store的时候通常会遇到这个问题

try again

很多人说这事苹果爸爸服务器问题，重复尝试几次，总会成功的！
但是经过尝试发现如果使用Application Loader上传成功率就非常高，所以还是推荐把ipa文件导出直接用Application Loader上传。
如果Application Loader也不行，需要检查下自己的网络，有时候vpn也会提高速度。

94、当tableView占不满一屏时，去除下边多余的单元格

self.tableView.tableHeaderView = [UIView new];self.tableView.tableFooterView = [UIView new];

95、isKindOfClass和isMemberOfClass的区别

isKindOfClass可以判断某个对象是否属于某个类，或者这个类的子类。isMemberOfClass更加精准，它只能判断这个对象类型是否为这个类(不能判断子类)

96、__block

当一个局部变量需要在block里改变时，需要在定义时加上__block修饰，具体请看官方文档 http://developer.apple.com/library/ios/documentation/cocoa/Conceptual/Blocks/Articles/bxVariables.html#//apple_ref/doc/uid/TP40007502-CH6-SW6

97、-[ViewController aMethod:]: unrecognized selector sent to instance 0x7fe91e607fb0

这是一个经典错误，ViewController不能响应aMethod这个方法，错误原因可能viewController文件中没有实现aMethod这个方法

98、UITableView (<UITableView: 0x7ff19b027000; >) failed to obtain a cell from its dataSource (<ViewController: 0x7ff19a507520>)

这个错误原因是tableView的代理方法-tableView:cellForRowAtIndexPath:需要返回一个UITableViewCell,而你返回了一个nil。另外这个地方返回值不是UITableViewCell类型也会导致崩溃

99、约束如何做UIView动画？

1、把需要改的约束Constraint拖条线出来，成为属性2、在需要动画的地方加入代码，改变此属性的constant属性3、开始做UIView动画，动画里边调用layoutIfNeeded方法@property (weak, nonatomic) IBOutlet NSLayoutConstraint *buttonTopConstraint;self.buttonTopConstraint.constant = 100;    [UIView animateWithDuration:.5 animations:^{        [self.view layoutIfNeeded];    }];

100、从NSURL中拿到链接字符串

NSString *urlString = myURL.absoluteString;

101、将tableView滚动到顶部

[tableView setContentOffset:CGPointZero animated:YES];或者[tableView scrollRectToVisible:CGRectMake(0, 0, 1, 1) animated:YES];

102、如果用addTarget:action:forControlEvents:方法为一个button添加了很多点击事件，在某个时刻想一次删除怎么办？只需要调用下边这句代码

[youButton removeTarget:nil action:nil forControlEvents:UIControlEventAllEvents];

103、某个字体的高度

font.lineHeight;

104、删除某个view所有的子视图

[[someView subviews] makeObjectsPerformSelector:@selector(removeFromSuperview)];

105、删除NSUserDefaults所有记录

//方法一  NSString *appDomain = [[NSBundle mainBundle] bundleIdentifier]; [[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];    //方法二  - (void)resetDefaults {     NSUserDefaults * defs = [NSUserDefaults standardUserDefaults];     NSDictionary * dict = [defs dictionaryRepresentation];     for (id key in dict) {          [defs removeObjectForKey:key];     }      [defs synchronize]; }// 方法三[[NSUserDefaults standardUserDefaults] setPersistentDomain:[NSDictionary dictionary] forName:[[NSBundle mainBundle] bundleIdentifier]];

106、禁用系统滑动返回功能

- (void)viewDidAppear:(BOOL)animated{     [super viewDidAppear:animated];if ([self.navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {self.navigationController.interactivePopGestureRecognizer.delegate = self;    }}- (void)viewWillDisappear:(BOOL)animated {    [super viewWillDisappear:animated];    if ([self.navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {self.navigationController.interactivePopGestureRecognizer.delegate = nil;    }}- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer{     return NO;}

107、模拟器报错

模拟器报错

解决办法：
打开模拟器->Simulator->Reset Content and Settings...
如果不行，就重启试试！

108、自定义cell选中背景颜色

UIView *bgColorView = [[UIView alloc] init];bgColorView.backgroundColor = [UIColor redColor];[cell setSelectedBackgroundView:bgColorView];

109、UILabel设置内边距

子类化UILabel，重写drawTextInRect方法- (void)drawTextInRect:(CGRect)rect {    // 边距，上左下右    UIEdgeInsets insets = {0, 5, 0, 5};    [super drawTextInRect:UIEdgeInsetsInsetRect(rect, insets)];}

110、UILabel设置文字描边

子类化UILabel，重写drawTextInRect方法- (void)drawTextInRect:(CGRect)rect{    CGContextRef c = UIGraphicsGetCurrentContext();    // 设置描边宽度    CGContextSetLineWidth(c, 1);    CGContextSetLineJoin(c, kCGLineJoinRound);    CGContextSetTextDrawingMode(c, kCGTextStroke);    // 描边颜色    self.textColor = [UIColor redColor];    [super drawTextInRect:rect];    // 文本颜色    self.textColor = [UIColor yellowColor];    CGContextSetTextDrawingMode(c, kCGTextFill);    [super drawTextInRect:rect];}

111、使用模拟器截图

快捷键command + s
或者File->Save Screen Shot

112、scrollView滚动到最下边

CGPoint bottomOffset = CGPointMake(0, scrollView.contentSize.height - scrollView.bounds.size.height);[scrollView setContentOffset:bottomOffset animated:YES];

113、UIView背景颜色渐变

    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 100)];    [self.view addSubview:view];    CAGradientLayer *gradient = [CAGradientLayer layer];    gradient.frame = view.bounds;    gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor blackColor] CGColor], (id)[[UIColor whiteColor] CGColor], nil];    [view.layer insertSublayer:gradient atIndex:0];

114、停止UIView动画

[yourView.layer removeAllAnimations]

115、为UIView某个角添加圆角

// 左上角和右下角添加圆角UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:view.bounds byRoundingCorners:(UIRectCornerTopLeft | UIRectCornerBottomRight) cornerRadii:CGSizeMake(20, 20)];    CAShapeLayer *maskLayer = [CAShapeLayer layer];    maskLayer.frame = view.bounds;    maskLayer.path = maskPath.CGPath;    view.layer.mask = maskLayer;

116、删除Xcode Derived data缓存数据

依次点击Xcode -> Preferences -> location，然后点击 Derived data路径后到小箭头，删除这个文件夹下的数据就可以了，如图

Xcode Derived data

117、将一个view放置在其兄弟视图的最上面

[parentView bringSubviewToFront:yourView]

118、将一个view放置在其兄弟视图的最下面

[parentView sendSubviewToBack:yourView]

119、让手机震动一下

倒入框架#import <AudioToolbox/AudioToolbox.h>AudioServicesPlayAlertSound(kSystemSoundID_Vibrate);或者AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);

120、layoutSubviews方法什么时候调用？

1、init方法不会调用
2、addSubview方法等时候会调用
3、bounds改变的时候调用
4、scrollView滚动的时候会调用scrollView的layoutSubviews方法(所以不建议在scrollView的layoutSubviews方法中做复杂逻辑)
5、旋转设备的时候调用
6、子视图被移除的时候调用
参考请看：http://blog.logichigh.com/2011/03/16/when-does-layoutsubviews-get-called/

121、让UILabel在指定的地方换行

// 换行符为\n,在需要换行的地方加上这个符号即可，如 label.numberOfLines = 0;label.text = @"此处\n换行";

122、摇一摇功能

1、打开摇一摇功能    [UIApplication sharedApplication].applicationSupportsShakeToEdit = YES;2、让需要摇动的控制器成为第一响应者[self becomeFirstResponder];3、实现以下方法// 开始摇动- (void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event// 取消摇动- (void)motionCancelled:(UIEventSubtype)motion withEvent:(UIEvent *)event// 摇动结束- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event

123、获取图片大小

CGFloat imageWidth = image.size.width;    CGFloat imageHeight = imageWidth * image.scale;

124、获取view的坐标在整个window上的位置

// v上的(0, 0)点在toView上的位置CGPoint point = [v convertPoint:CGPointMake(0, 0) toView:[UIApplication sharedApplication].windows.lastObject];或者CGPoint point = [v.superview convertPoint:v.frame.origin toView:[UIApplication sharedApplication].windows.lastObject];

125、提交App Store审核程序限制

您的应用程序的未压缩大小必须小于4GB。每个Mach-O可执行文件（例如app_name.app/app_name）不能超过这些限制：
对于MinimumOSVersion小于7.0的应用程序：TEXT二进制文件中所有部分的总数最多为80 MB 。
对于MinimumOSVersion7.x到8.x的应用程序：TEXT对于二进制文件中每个体系结构片段的每个片段，最大为60 MB 。
对于MinimumOSVersion9.0或更高版本的应用程序：__TEXT二进制文件中所有部分的总数最多为500 MB 。参阅：iTunes Connect开发者指南

126、修改UISegmentedControl的字体大小

[segment setTitleTextAttributes:@{NSFontAttributeName : [UIFont systemFontOfSize:15.0f]} forState:UIControlStateNormal];

127、在非ViewController的地方弹出UIAlertController对话框

//  最好抽成一个分类UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Title" message:@"message" preferredStyle:UIAlertControllerStyleAlert];//...id rootViewController = [UIApplication sharedApplication].delegate.window.rootViewController;if([rootViewController isKindOfClass:[UINavigationController class]]){    rootViewController = ((UINavigationController *)rootViewController).viewControllers.firstObject;}if([rootViewController isKindOfClass:[UITabBarController class]]){    rootViewController = ((UITabBarController *)rootViewController).selectedViewController;}[rootViewController presentViewController:alertController animated:YES completion:nil];

128、获取一个view所属的控制器

// view分类方法- (UIViewController *)belongViewController {    for (UIView *next = [self superview]; next; next = next.superview) {        UIResponder* nextResponder = [next nextResponder];        if ([nextResponder isKindOfClass:[UIViewController class]]) {            return (UIViewController *)nextResponder;        }    }    return nil;}

129、UIImage和base64互转

// view分类方法- (NSString *)encodeToBase64String:(UIImage *)image { return [UIImagePNGRepresentation(image) base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];}- (UIImage *)decodeBase64ToImage:(NSString *)strEncodeData {  NSData *data = [[NSData alloc]initWithBase64EncodedString:strEncodeData options:NSDataBase64DecodingIgnoreUnknownCharacters];  return [UIImage imageWithData:data];}

130、UIWebView设置背景透明

[webView setBackgroundColor:[UIColor clearColor]];[webView setOpaque:NO];

131、判断NSDate是不是今天

NSDateComponents *otherDay = [[NSCalendar currentCalendar] components:NSCalendarUnitEra | NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay fromDate:aDate];NSDateComponents *today = [[NSCalendar currentCalendar] components:NSCalendarUnitEra | NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay fromDate:[NSDate date]];if([today day] == [otherDay day] &&   [today month] == [otherDay month] &&   [today year] == [otherDay year] &&   [today era] == [otherDay era]) {    // 是今天}

132、设置tableView分割线颜色

[self.tableView setSeparatorColor:[UIColor myColor]];

133、设置屏幕方向

[[UIDevice currentDevice] setValue:@(UIInterfaceOrientationLandscapeLeft) forKey:@"orientation"];

134、比较两个颜色是否相等

- (BOOL)isEqualToColor:(UIColor *)otherColor {    CGColorSpaceRef colorSpaceRGB = CGColorSpaceCreateDeviceRGB();    UIColor *(^convertColorToRGBSpace)(UIColor*) = ^(UIColor *color) {        if (CGColorSpaceGetModel(CGColorGetColorSpace(color.CGColor)) == kCGColorSpaceModelMonochrome) {            const CGFloat *oldComponents = CGColorGetComponents(color.CGColor);            CGFloat components[4] = {oldComponents[0], oldComponents[0], oldComponents[0], oldComponents[1]};            CGColorRef colorRef = CGColorCreate( colorSpaceRGB, components );            UIColor *color = [UIColor colorWithCGColor:colorRef];            CGColorRelease(colorRef);            return color;                    } else            return color;    };    UIColor *selfColor = convertColorToRGBSpace(self);    otherColor = convertColorToRGBSpace(otherColor);    CGColorSpaceRelease(colorSpaceRGB);    return [selfColor isEqual:otherColor];}

135、tableViewCell分割线顶到头

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {    [cell setSeparatorInset:UIEdgeInsetsZero];    [cell setLayoutMargins:UIEdgeInsetsZero];    cell.preservesSuperviewLayoutMargins = NO;}- (void)viewDidLayoutSubviews {    [self.tableView setSeparatorInset:UIEdgeInsetsZero];    [self.tableView setLayoutMargins:UIEdgeInsetsZero];}

136、不让控制器的view随着控制器的xib拉伸或压缩

self.view.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

137、cocoaPods报错 : [!] Unable to add a source with url https://github.com/CocoaPods/Specs.git namedmaster-1.

You can try adding it manually in ~/.cocoapods/repos or via pod repo add.

解决方法：这是因为电脑里安装了另外一个Xcode导致cocoapods找不到路径了
在终端执行 sudo xcode-select -switch /Applications/Xcode.app 即可

138、安装cocoapods的时候出现 ERROR: While executing gem ... (Errno::EPERM)

Operation not permitted - /usr/bin/pod

解决办法：直接在终端执行 sudo gem install -n /usr/local/bin cocoapods

139、在状态栏增加网络请求的菊花，类似safari加载网页的时候状态栏菊花

[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;

140、检查一个rect是否包含一个point

// point是否在rect内BOOL isContains = CGRectContainsPoint(rect, point);

141、在指定的宽度下，让UILabel自动设置最佳font

label.adjustsFontSizeToFitWidth = YES;

142、将一个image保存在相册中

UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);或者#import <Photos/Photos.h>[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{        PHAssetChangeRequest *changeRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:image];        changeRequest.creationDate          = [NSDate date];    } completionHandler:^(BOOL success, NSError *error) {        if (success) {            NSLog(@"successfully saved");        }        else {            NSLog(@"error saving to photos: %@", error);        }    }];

143、修改cell.imageView的大小

UIImage *icon = [UIImage imageNamed:@""];CGSize itemSize = CGSizeMake(30, 30);UIGraphicsBeginImageContextWithOptions(itemSize, NO ,0.0);CGRect imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height);[icon drawInRect:imageRect];cell.imageView.image = UIGraphicsGetImageFromCurrentImageContext();UIGraphicsEndImageContext();

144、为一个view添加虚线边框

 CAShapeLayer *border = [CAShapeLayer layer];    border.strokeColor = [UIColor colorWithRed:67/255.0f green:37/255.0f blue:83/255.0f alpha:1].CGColor;    border.fillColor = nil;    border.lineDashPattern = @[@4, @2];    border.path = [UIBezierPath bezierPathWithRect:view.bounds].CGPath;    border.frame = view.bounds;    [view.layer addSublayer:border];

145、UITextView中打开或禁用复制，剪切，选择，全选等功能

// 继承UITextView重写这个方法- (BOOL)canPerformAction:(SEL)action withSender:(id)sender{// 返回NO为禁用，YES为开启    // 粘贴    if (action == @selector(paste:)) return NO;    // 剪切    if (action == @selector(cut:)) return NO;    // 复制    if (action == @selector(copy:)) return NO;    // 选择    if (action == @selector(select:)) return NO;    // 选中全部    if (action == @selector(selectAll:)) return NO;    // 删除    if (action == @selector(delete:)) return NO;    // 分享    if (action == @selector(share)) return NO;    return [super canPerformAction:action withSender:sender];}