IOS开发之OC学习笔记(中)

• 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
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• 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-结构体

用法参考：

NSRange range = NSMakeRange(8, 10);
CGPoint p = NSMakePoint(10, 9);
NSPoint p = CGPointMake(8, 9);
NSSize size = NSMakeSize(90, 80);
CGSize size = CGSizeMake(10, 8);
NSRect rect = = NSMakeRect(10, 10, 80, 80);
CGRect rect = CGRectMake(8, 9, 10, 90);
类型打印方式：NSLog(@”%@”, NSStringFromRect(rect));

2. Foundation-NSString

NSString的创建

// 这种方式创建出来的字符串是不需要释放的NSString *str1 = @"A String!";NSString *str2 = [[NSString alloc] init];str2 = @"A String!";[str2 release];//将c语言的字符转NSStringNSString *str4 = [[NSString alloc] initWithUTF8String:"A String!"];[str4 release];str4 = [NSString stringWithUTF8String:"A String!"];str5 = [NSString stringWithFormat:@"My age is %i and height is %.2f", 19, 1.55f];

从文件、网络读取文本

NSString *path = @"/Users/apple/Desktop/test.txt";// 这个方法已经过期，不能解析中文// NSString *str1 = [NSString stringWithContentsOfFile:path];// 定义一个NSError变量NSError *error;// 指定字符串编码为UTF-8: NSUTF8StringEncodingNSString *str1 = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:&error];if (error == nil) { // 没有错误信息    NSLog(@"读取文件成功：%@", str1);} else {    NSLog(@"读取文件失败：%@", error);}NSURL *url = [NSURL URLWithString:@"file:///Users/apple/Desktop/test.txt"];NSString *str2 = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];NSLog(@"%@", str2);NSURL *url2 = [NSURL URLWithString:@"http://www.baidu.com"];NSString *str3 = [NSString stringWithContentsOfURL:url2 encoding:NSUTF8StringEncoding error:nil];NSLog(@"%@", str3);

字符串的导出

NSString *str = @"123456我是字符串！！！！";// 如果文件不存在，会自动创建文件// 如果文件夹不存在，会直接报错NSString *path = @"/Users/apple/Desktop/abc.txt";NSError *error;// 编码指定错误也会报错// YES代表要进行原子性操作，也就是会创建一个中间的临时文件[str writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:&error];if (error) {    // [error localizedDescription]会返回主要的错误信息    NSLog(@"写入失败：%@", [error localizedDescription]);//???} else {    NSLog(@"写入成功");}

大小写转换

NSString *str = @"GuangDong";NSLog(@"大写：%@", [str uppercaseString]);NSLog(@"小写：%@", [str lowercaseString]);// 首字母变大写，其他字母变小写NSLog(@"首字母变大写：%@", [@"aGE" capitalizedString]);

字符串的比较

// 检测字符串的内容是否相同BOOL result = [@"abc" isEqualToString:@"abc"];NSLog(@"%i", result);NSLog(@"'a' =%i ,'A' = %i", 'a','A');//'a' =97 ,'A' = 65// NSOrderedAscending  右边的字符串比左边大// NSOrderedSame  两个字符串的内容相同// NSOrderedDescending  左边的字符串比右边的大NSComparisonResult result2 = [@"abc" compare:@"Abc"];if (result2 == NSOrderedSame) {    NSLog(@"两个字符串的内容相同");} else if (result2 == NSOrderedAscending) {    NSLog(@"右边 > 左边");} else if (result2 == NSOrderedDescending) {    NSLog(@"右边 < 左边");}//右边 < 左边

字符串的搜索

NSString *str = @"123456456.txt";NSLog(@"是否以22开头：%i", [str hasPrefix:@"22"]);//0NSLog(@"是否以txt结尾：%i", [str hasSuffix:@"txt"]);//1// 搜索字符串NSRange range = [str rangeOfString:@"456"];// range.length == 0if (range.location == NSNotFound) {    NSLog(@"不能找到");} else {    NSLog(@"找到的范围是：%@", NSStringFromRange(range));//{3, 3}}// 从尾部开始搜索字符串range = [str rangeOfString:@"456" options:NSBackwardsSearch];NSLog(@"从尾部开始搜索:%@", NSStringFromRange(range));//{6, 3}// 指定范围进行搜索range = [str rangeOfString:@"456" options:NSBackwardsSearch range:(NSMakeRange(2, 6))];NSLog(@"指定范围进行搜索:%@", NSStringFromRange(range));//{3, 3}

字符串的截取

NSString *str = @"123456";// 从索引3开始截取到尾部(包括3)NSLog(@"%@", [str substringFromIndex:3]);//456// 从头部开始截取到索引3之前(不包括3)NSLog(@"%@", [str substringToIndex:3]);//123// 指定范围进行截取NSRange range = NSMakeRange(2, 3);NSLog(@"%@", [str substringWithRange:range]);//345NSString *str2 = @"a-b-c-d-5";NSArray *array = [str2 componentsSeparatedByString:@"-"];NSLog(@"%@", array);//(a,b,c,d,5)NSString *str3 =  [array objectAtIndex:0];NSLog(@"%@", str3);//a

与路径相关

// 快速创建一个自动释放的数组NSMutableArray *components = [NSMutableArray array];[components addObject:@"Users"];[components addObject:@"MJ"];[components addObject:@"Desktop"];// 将数组中的所有字符串拼接成一个路径NSString *path = [NSString pathWithComponents:components];NSLog(@"%@", path);//Users/MJ/Desktop// 将路径分解成一个数组NSArray *cmps = [path pathComponents];NSLog(@"%@", cmps);//(Users,MJ,Desktop)// path是一个字符串常量，是不可变的path = @"/users/mj/test";// 判断是够为绝对路径（依据是前面有无/）NSLog(@"%i", [path isAbsolutePath]);//1NSLog(@"最后一个目录：%@", [path lastPathComponent]);//test// 删除最后一个目录NSLog(@"%@", [path stringByDeletingLastPathComponent]);///users/mj// 在最后面拼接一个目录NSLog(@"%@", [path stringByAppendingPathComponent:@"abc"]);///users/mj/test/abc

拓展名处理

NSString *str = @"/User/MJ/test.txt";NSLog(@"拓展名：%@", [str pathExtension]);//txt// 删除拓展名NSLog(@"%@", [str stringByDeletingPathExtension]);///User/MJ/test// 添加拓展名NSLog(@"%@", [@"abc" stringByAppendingPathExtension:@"mp3"]);//abc.mp3

其他用法

//NSString 转intNSString *str = @"12";int a = [str intValue];NSLog(@"%i", a);//12// 计算字数，不是计算字符数NSLog(@"length=%zi", [@"我是字符串123" length]);//length=8// 取出对应的字符unichar c = [@"abc" characterAtIndex:0];NSLog(@"%c", c);// 返回C语言中的字符串const char *s = [@"abc" UTF8String];NSLog(@"%s", s);//abc

3. Foundation-NSMutableString

可变字符串的创建

// 预先分配10个字数的存储空间NSMutableString *str = [[NSMutableString alloc] initWithCapacity:10];//this is okNSMutableString *str = [[NSMutableString alloc]init];// 设置字符串内容[str setString:@"1234"];// 拼接一个字符串[str appendString:@"567"];// 拼接字符串[str appendFormat:@"age is %i and height is %.2f", 27, 1.55f];//1234567age is 27 and height is 1.55// 替换字符串NSRange range = [str rangeOfString:@"height"];//NSRange range = NSMakeRange(7, 3);[str replaceCharactersInRange:range withString:@"no"];//1234567age is 27 and no is 1.55// 插入字符串[str insertString:@"abc" atIndex:2];//12abc34567age is 27 and no is 1.55// 删除字符串range = [str rangeOfString:@"age"];[str deleteCharactersInRange:range];NSLog(@"%@", str);//12abc34567 is 27 and no is 1.55// 释放对象[str release];

4. Foundation-NSArray

创建一个数组

// 创建一个空的数组NSArray *array = [NSArray array];// 创建有1个元素的数组array = [NSArray arrayWithObject:@"123"];// 创建有多个元素的数组array = [NSArray arrayWithObjects:@"a", @"b", @"c", nil]; //count = 3int count = [array count];// count = array.count;NSLog(@"%i", count);

数组的简单使用

NSObject *obj = [[NSObject alloc] init];NSArray *array = [NSArray arrayWithObjects:@"a", @"b", @"c" , obj, nil];// 判断是否包含了某个元素if ([array containsObject:@"a"]) {    NSLog(@"包含了字符串a");}NSString *last = [array lastObject];NSLog(@"last=%@", last);//NSString *str = [array objectAtIndex:1];NSLog(@"%@", str);int index = [array indexOfObject:@"c"];NSLog(@"index=%i", index);[obj release];

数组的内存管理

Student *stu1 = [[Student alloc] init];Student *stu2 = [[Student alloc] init];Student *stu3 = [[Student alloc] init];NSLog(@"stu1:%zi", [stu1 retainCount]);//1// 当把一个对象塞进数组中时，这个对象的计数器会加1，也就是说数组会对它做一次retain操作NSArray *array = [[NSArray alloc] initWithObjects:stu1, stu2, stu3, nil];NSLog(@"stu1:%zi", [stu1 retainCount]);//2NSLog(@"count=%zi", array.count);//3[stu1 release];//1[stu2 release];[stu3 release];// 数组被销毁的时候，会对内部的所有元素都做一次release操作[array release];//0

给数组里面的元素发送消息

Student *stu1 = [Student student];Student *stu2 = [Student student];Student *stu3 = [Student student];NSArray *array = [NSArray arrayWithObjects:stu1, stu2, stu3, nil];// 让数组里面的所有对象都调用test方法 [array makeObjectsPerformSelector:@selector(test)];// 让数组里面的所有对象都调用tes2t方法,并传递一个[array makeObjectsPerformSelector:@selector(test2:) withObject:@"123"];

遍历数组

Student *stu1 = [Student student];NSArray *array = [NSArray arrayWithObjects:stu1, @"1", @"2", @"3", nil];//方法1int count = array.count;for (int i = 0; i<count; i++) {    // id == void *    id obj = [array objectAtIndex:i];    NSLog(@"%i-%@", i, obj);}//方法2// 快速遍历int i =0;for (id obj in array) {    NSLog(@"%i-%@", i, obj);    i++;}//方法3[array enumerateObjectsUsingBlock: ^(id obj, NSUInteger idx, BOOL *stop) {    NSLog(@"%i-%@", idx, obj);     // 如果索引为1，就停止遍历     if (idx == 1) {         // 利用指针修改外面BOOL变量的值         *stop = YES;     }}];//方法3输出：//0-<Student: 0x100102e40>//1-1//方法4// 获取数组的迭代器// NSEnumerator *enumerator = [array objectEnumerator];// 反序迭代器（从尾部开始遍历元素）NSEnumerator *enumerator = [array reverseObjectEnumerator];// allObjects是取出没有被遍历过的对象NSArray *array2 = [enumerator allObjects];NSLog(@"array2:%@", array2);// 获取下一个需要遍历的元素id obj = nil;while (obj = [enumerator nextObject]) {    NSLog(@"obj=%@", obj);}

派生出新的数组

NSArray *array = [NSArray arrayWithObjects:@"1", @"2", nil];NSArray *array2 = [array arrayByAddingObject:@"3"];NSArray *array3 = [array arrayByAddingObjectsFromArray:[NSArray arrayWithObjects:@"4", @"5", nil]];NSLog(@"array:%@", array);//(1,2)NSLog(@"array2:%@", array2);//(1,2,3)NSLog(@"array3:%@", array3);//(1,2,4,5)NSArray *array4 = [NSArray arrayWithObjects:@"1", @"2", @"3", @"4", nil];NSRange range = NSMakeRange(1, 2);NSArray *array5 = [array4 subarrayWithRange:range];NSLog(@"array5:%@", array5);//(2,3)

数组的其他用法

NSArray *array = [NSArray arrayWithObjects:@"1", @"2", @"3", @"4", nil];// 1-2-3-4// 利用分隔符-拼接所有的数组元素NSString *str = [array componentsJoinedByString:@"-"];NSLog(@"%@", str);// 将一个数组写入文件（生成的是一个xml文件）NSString *path = @"/Users/apple/Desktop/array.xml";[array writeToFile:path atomically:YES];path = @"/Users/apple/Desktop/array.txt";//上面写入的xml文件，此处也可以直接读取// 从文件中读取数组内容（文件有严格的格式要求）,格式如下//<array>//  <string>1</string>//  <string>2</string>//  <string>3</string>//  <string>4</string>//</array>NSArray *array2 = [NSArray arrayWithContentsOfFile:path];NSLog(@"array2:%@", array2);

数组排序

• 排序1

NSArray *array = [NSArray arrayWithObjects:@"2", @"3", @"1", @"4", nil];// 返回一个排好序的数组，原来数组的元素顺序不会改变// 指定元素的比较方法：compare:// compare two NSDecimalNumbersNSArray *array2 = [array sortedArrayUsingSelector:@selector(compare:)];NSLog(@"array2:%@", array2);//(1,2,3,4)

• 排序2、3

Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li"];Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang"];Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li"];Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao"];NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil];方法1// 指定排序的比较方法NSArray *array2 = [array sortedArrayUsingSelector:@selector(compareStudent:)];//compareStudent 是什么，见下一个代码块//方法2// 利用block进行排序NSArray *array2 = [array sortedArrayUsingComparator: ^NSComparisonResult(Student *obj1, Student *obj2) {     // 先按照姓排序     NSComparisonResult result = [obj1.lastname compare:obj2.lastname];     // 如果有相同的姓，就比较名字     if (result == NSOrderedSame) {         result = [obj1.firstname compare:obj2.firstname];     }     return result;}];NSLog(@"array2:%@", array2);//("[Huang LongHu-(null)]","[Li LianJie-(null)]","[Li MingJie-(null)]","[Xiao Jian-(null)]")

其中compareStudent是Student的一个方法，如下：- (NSComparisonResult)compareStudent:(Student *)stu {    // 先按照姓排序    NSComparisonResult result = [self.lastname compare:stu.lastname];    // 如果有相同的姓，就比较名字    if (result == NSOrderedSame) {        result = [self.firstname compare:stu.firstname];    }    return result;}

• 排序4

Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li" bookName:@"book1"];Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang" bookName:@"book2"];Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li" bookName:@"book2"];Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao" bookName:@"book1"];NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil];// 1.先按照书名进行排序// 这里的key写的是@property的名称NSSortDescriptor *bookNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"book.name" ascending:YES];// 2.再按照姓进行排序NSSortDescriptor *lastnameDesc = [NSSortDescriptor sortDescriptorWithKey:@"lastname" ascending:YES];// 3.再按照名进行排序NSSortDescriptor *firstnameDesc = [NSSortDescriptor sortDescriptorWithKey:@"firstname" ascending:YES];// 按顺序添加排序描述器NSArray *descs = [NSArray arrayWithObjects:bookNameDesc, lastnameDesc, firstnameDesc, nil];NSArray *array2 = [array sortedArrayUsingDescriptors:descs];NSLog(@"array2:%@", array2);//("[Li MingJie-book1]","[Xiao Jian-book1]","[Huang LongHu-book2]","[Li LianJie-book2]")

5. Foundation-NSMutableArray

用法如下

NSMutableArray *array = [NSMutableArray arrayWithObject:@"1"];// 添加元素[array addObject:@"2"];[array addObject:@"3"];//移除元素[array removeObject:@"2"];[array removeLastObject];[array removeAllObjects];//替换元素[array replaceObjectAtIndex:1 withObject:@"4"];//排序[array sortUsingSelector:@selector(compare:)];//此处array发生变化，区别NSArray

NSMutableArray的内存管理

NSMutableArray *array = [[NSMutableArray alloc] init];Student *stu1 = [[Student alloc] init];// stu1:1stu1.age = 10;Student *stu2 = [[Student alloc] init];// stu2:1stu2.age = 20;// 对被添加的元素做一次retain操作，计数器+1[array addObject:stu1]; // stu1:2[array addObject:stu2]; // stu2:2NSLog(@"add->stu1:%zi", [stu1 retainCount]);// 对被删除的元素做一次release操作，计数器-1[array removeObject:stu1]; // stu1:1NSLog(@"remove->stu1:%zi", [stu1 retainCount]);// 释放学生[stu1 release]; // stu1:0[stu2 release]; // stu2:1// 当数组被释放的时候，会对所有的元素都做一次release操作[array release]; // stu2:0