[oc学习日记]字典

来源：互联网发布：安全座椅选择知乎编辑：程序博客网时间：2024/06/14 00:35
  //字典的创建 2         NSDictionary *d1 = [NSDictionary dictionary]; 3         //将创建的字典的内容设置为制定的文件的内容 4         NSString *path = @"";//文件路径 5         NSDictionary *d2 = [NSDictionary dictionaryWithContentsOfFile:path]; 6         //创建具有一个键值的字典 7         NSDictionary *d3 = [NSDictionary dictionaryWithObject:@"s" forKey:@"s"]; 8         //创建具有多个键值的字典  键值对必需对应 9         //值在前  键在后10         NSDictionary *d4 = [NSDictionary dictionaryWithObjectsAndKeys:@"ss",@"2",11                                          @"ss",@"1",12                                          nil];13         14         //利用数组创建字典15         NSArray *key = @[@"2",@"3",@"4"];16         NSArray *obj = @[@"ss",@"ff",@"gg"];17         NSDictionary *d5 = [NSDictionary dictionaryWithObjects:obj forKeys:key];18         //便捷方式19         //键在前 值在后20         NSDictionary *d6 = @{21                              @"2":@"d",22                              @"3":@"d"};23         24         //init初始化25         //将初始化的字典内容设置为指定文件内容26         NSDictionary *dd = [[NSDictionary alloc]initWithContentsOfFile:path];27         //初始化具有多个键-值的字典(利用数组)28         NSDictionary *dd1 = [[NSDictionary alloc]initWithObjects:obj forKeys:key];29         //初始化具有多个键-值的字典30         NSDictionary *dd2 = [[NSDictionary alloc]initWithObjectsAndKeys:31         @"ss",@"2",32         @"ss",@"1", nil];33         34         35         36         //字典基本操作37         //字典是无序的  键不可以重复 值可以重复38         //返回所有键39         NSLog(@"%@",[dd2 allKeys]);40         //返回所有值41         NSLog(@"%@",[dd2 allValues]);42         //返回所有值对应的键43         NSLog(@"%@",[dd2 allKeysForObject:@"ss"]);44         //返回对应键的值  最常见 最重要45         NSLog(@"%@",[dd2 objectForKey:@"ss"]);46         //键值对47         NSLog(@"%zi",dd2.count);48 49         50         //不可变字典51         //创建52         NSMutableDictionary *dic = [NSMutableDictionary dictionary];53         //分配空间54         NSMutableDictionary *dic1 = [[NSMutableDictionary alloc]initWithCapacity:10];55         //创建并赋值56         NSMutableDictionary *dic2 = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"ss",@"2",57                                      @"ss",@"1", nil];58         //添加键值对59         [dic2 setObject:@"s" forKey:@"sdads"];60         //删除所有键值对61         [dic2 removeAllObjects];62         //删除指定键对应的键值对63         [dic2 removeObjectForKey:@"sd"];64         65         66         //字典的遍历67         //快速遍历68         for (id key in dic2) {69             NSLog(@"%@ = %@",key,[dic2 objectForKey:key]);70         }71         //代码块遍历72         [dic2 enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {73             NSLog(@"%@ %@",key,obj);74         }];75         //迭代器遍历76         //可以输出键和值77         NSEnumerator *en = [dic2 keyEnumerator];//将所有键装入数组78         id key2 = nil;79         while (key2 = [en nextObject]) {80             NSLog(@"%@ %@",key2,[dic2 objectForKey:key2]);81         }82         NSEnumerator *en1 = [dic2 objectEnumerator];//将所有值装入数组83         //只可以输出值84         id obj3 = nil;85         while (obj3 = [en1 nextObject]) {86             NSLog(@"%@", obj);87         }88         89         90         //键给空值会异常   值给控制就是结束标志
补充一点：
如果将自定义的类对象封装进字典
可以用setValuesForKeysWithDictionary方法对对象属性进行赋值，但是封装进字典的键一定要和类中的属性名相同，并且数量不能超过类中的属性数量
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