IOS开发之OC学习笔记(下)

• 该笔记源自本人对一个网络视频的学习
• 百度网盘链接 ，密码: tp3a
• 如有侵权，请联系本人删除。
• 都是比较基础的OC知识，中高级开发者可以忽略本文
• 很多重要内容在代码注释中

1. Foundation-NSDictionary

字典的初始化：

    // NSDictionary是不可变的    NSDictionary *dict = [NSDictionary dictionaryWithObject:@"v" forKey:@"k"];    //{k = v;}    // 最常用的初始化方式    dict = [NSDictionary dictionaryWithObjectsAndKeys:            @"v1", @"k1",            @"v2", @"k2",            @"v3", @"k3", nil];    NSArray *objects = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil];    NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil];    dict = [NSDictionary dictionaryWithObjects:objects forKeys:keys];//    {k1 = v1;k2 = v2;k3 = v3;}    NSLog(@"%@", dict);

字典的基本用法：

• 有多少个键值对(key-value)
  dict.count

• 由于NSDictionary是不可变的，所以只能取值，而不能修改值
  id obj = [dict objectForKey:@"k2"];

• 将字典写入文件中
  NSString *path = @"/Users/apple/Desktop/dict.xml";
[dict writeToFile:path atomically:YES];

• 从文件中读取内容
  dict = [NSDictionary dictionaryWithContentsOfFile:path];

• 返回所有的key或者value
  NSArray *keys = [dict allKeys];
NSArray *objects = [dict allValues];

• 根据多个key取出对应的多个value
  当key找不到对应的value时，用marker参数值代替
  objects = [dict objectsForKeys:[NSArray arrayWithObjects:@"k1", @"k2", @"k4", nil] notFoundMarker:@"not-found"];
  结果：objects= (v1,v2,”not-found”)

遍历字典的所有key或者value：

//方法一 for循环for (id key in dict) {    id value = [dict objectForKey:key];    NSLog(@"%@=%@", key, value);}

//方法二 key迭代器NSEnumerator *enumer = [dict keyEnumerator];id key = nil;while ( key = [enumer nextObject]) {    id value = [dict objectForKey:key];    NSLog(@"%@=%@", key, value);}//k3=v3   k2=v2   k1=v1for (NSObject *object in [dict objectEnumerator]) {    NSLog(@"对象迭代器遍历的值: %@",object);}//v3 v2 v1 

//方法三 use block[dict enumerateKeysAndObjectsUsingBlock: ^(id key, id obj, BOOL *stop) {    NSLog(@"%@=%@", key, obj);}];

字典的内存管理：

Student *stu1 = [Student studentWithName:@"stu1"];Student *stu2 = [Student studentWithName:@"stu2"];Student *stu3 = [Student studentWithName:@"stu3"];// 一个对象称为字典的key或者value时，会做一次retain操作，也就是计数器会+1NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:                      stu1, @"k1",                      stu2, @"k2",                      stu3, @"k3", nil];// 当字典被销毁时，里面的所有key和value都会做一次release操作，也就是计数器会-1

2. Foundation-NSMUtableDictonary

可变字典的使用

// 创建一个空的字典NSMutableDictionary *dict = [NSMutableDictionary dictionary];Student *stu1 = [Student studentWithName:@"stu1"];Student *stu2= [Student studentWithName:@"stu2"];// 添加元素// stu1的计数器会+1[dict setObject:stu1 forKey:@"k1"];NSLog(@"stu1:%zi", [stu1 retainCount]);// 添加其他字典other到当前字典dict中NSDictionary *other = [NSDictionary dictionaryWithObject:@"v2" forKey:@"k2"];[dict addEntriesFromDictionary:other];// 删除所有的键值对// [dict removeAllObjects];// 删除k1对应的元素stu1，stu1会做一次release操作[dict removeObjectForKey:@"k1"];NSLog(@"stu1:%zi", [stu1 retainCount]);// 删除多个key对应的value// [dict removeObjectsForKeys:[NSArray arrayWithObject:@"k1"]];// 字典被销毁时，内部的所有key和value计数器都会-1，也就是说stu1会release一次

3. Foundation-NSNumber

// 将int类型的10 包装成 一个NSNumber对象NSNumber *number = [NSNumber numberWithInt:10];NSLog(@"number=%@", number);// 添加数值到数组中NSMutableArray *array = [NSMutableArray array];[array addObject:number];// 取出来还是一个NSNumber对象，不支持自动解包(也就是不会自动转化为int类型)NSNumber *number1 = [array lastObject];// 将NSNumber转化成int类型int num = [number1 intValue];NSLog(@"num=%i", num);

4. Foundation-NSValue

将结构体变量包装成一个对象

CGPoint point = CGPointMake(10, 10);NSValue *value = [NSValue valueWithPoint:point];NSMutableArray *array = [NSMutableArray array];[array addObject:value];// 添加value// 取出当时放进去的valueNSValue *value1 = [array lastObject];CGPoint point1 = [value1 pointValue];BOOL result = CGPointEqualToPoint(point1, point);

typedef struct {    int year;    int month;    int day;} Date;void value2() {    Date date = {2013, 4, 7};    // 这里要传结构体的地址&date    // 根据结构体类型生成 对应的 类型描述字符串    char *type = @encode(Date);    NSValue *value = [NSValue value:&date withObjCType:type];    Date date1;// 定义一个结构体变量    [value getValue:&date1];// 取出包装好的结构体    // [value objCType];  取出类型描述字符串    NSLog(@"year=%i, month=%i, day=%i", date1.year, date1.month, date1.day);    //year=2013, month=4, day=7}

5. Foundation-NSNull

// [NSNull null]返回的是同一个单粒对象NSNull *n = [NSNull null];NSNull *n1 = [NSNull null];NSLog(@"%i", n == n1);//1

6. Foundation-NSDate

日期创建

// date方法返回的就是当前时间(now)NSDate *date = [NSDate date];NSLog(@"11:%@", date);//11:2016-04-06 14:42:19 +0000// now:  11:12:40// date: 11:12:50date = [NSDate dateWithTimeIntervalSinceNow:10];NSLog(@"22:%@", date);//22:2016-04-06 14:42:29 +0000// 从1970-1-1 00:00:00开始date = [NSDate dateWithTimeIntervalSince1970:10];NSLog(@"33:%@", date);//33:1970-01-01 00:00:10 +0000// 随机返回一个比较遥远的未来时间date = [NSDate distantFuture];NSLog(@"44:%@", date);//44:4001-01-01 00:00:00 +0000// 随机返回一个比较遥远的过去时间date = [NSDate distantPast];NSLog(@"55:%@", date);//55:0000-12-30 00:00:00 +0000

日期使用

NSDate *date = [NSDate date];// 返回1970-1-1开始走过的毫秒数NSTimeInterval interval = [date timeIntervalSince1970];NSLog(@"interval = %f",interval);//1459954262.860866NSDate *date2 = [NSDate date];// 返回比较早的那个时间NSLog(@"%@",[date earlierDate:date2]);//2016-04-06 14:51:02 +0000// 返回比较晚的那个时间NSLog(@"%@",[date laterDate:date2]);//2016-04-06 14:51:02 +0000// 跟其他时间进行对比interval =[date2 timeIntervalSinceDate:date];NSLog(@"interval = %f",interval);//0.001233

日期格式化

NSDate *date = [NSDate date];NSDateFormatter *formatter = [[NSDateFormatter alloc] init];// HH是24进制，hh是12进制formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";//修正stringFromDate时区差异//formatter.locale = [[[NSLocale alloc] initWithLocaleIdentifier:@"zh_CN"] autorelease];NSString *string = [formatter stringFromDate:date];NSLog(@"%@", string);// 返回的格林治时间NSDate *date2 = [formatter dateFromString:@"2010-09-09 13:14:56"];NSLog(@"%@", date2);//2010-09-09 05:14:56 +0000[formatter release];

7. Foundation-NSObject

NSObject使用

• isKindOfClass判断对象是否属于某个类 或者 子类
  if ( [stu isKindOfClass:[Person class]] ) {
// NSLog(@"stu属于Person或者继承自Person");}
• isMemberOfClass判断对象是否属于某个类（不包括子类）
  BOOL result = [stu isMemberOfClass:[Student class]];
• 直接调用
  [stu test];
• 间接调用
  [stu performSelector:@selector(test)];
[stu performSelector:@selector(test2:) withObject:@"abc"];
• 延迟2秒后调用test2:方法
  [stu performSelector:@selector(test2:) withObject:@"abc" afterDelay:2];

反射的使用

// 类的反射NSString *str = @"Person";Class class = NSClassFromString(str);Person *person = [[class alloc] init];NSLog(@"%@", person);//<Person: 0x100300320>// Class变成字符串NSString *name =  NSStringFromClass([Person class]);NSLog(@"%@", name);//Person// 方法的反射NSString *method = @"test";SEL selector = NSSelectorFromString(method);[person performSelector:selector];//调用了Person的test方法// 将SEL转换为字符串NSString *selectorName = NSStringFromSelector(selector); NSLog(@"%@", selectorName);//test[person release];