Dictionary的用法

atomically:原子性，当文件内容写入成功之后再创建文件。

NSArray *keys = [NSArray arrayWithObjects:@"name", @"age", nil];
NSArray *values = [NSArray arrayWithObjects:@"wzx", [NSNumber numberWithInt:16], nil];
NSDictionary *dict = [NSDictionary dictionaryWithObjects:values forKeys:keys];

    // NSDictionary是不可变的
   NSDictionary *dict = [NSDictionary dictionaryWithObject:@"v" forKey:@"k"];
    
    // 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];
    NSLog(@"%@", dict);


    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
            @"v1", @"k1",
            @"v2", @"k2",
            @"v3", @"k3", nil];
    
    // count是计算有多少个键值对(key-value)
    NSLog(@"count=%zi", 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"];
    NSLog(@"obj=%@", obj);

    // 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];
    NSLog(@"dict=%@", dict);


   NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"v1", @"k1",
                          @"v2", @"k2",
                          @"v3", @"k3", nil];
    // 返回所有的key
    NSArray *keys = [dict allKeys];
    //NSLog(@"keys=%@", keys);
    
    NSArray *objects = [dict allValues];
    //NSLog(@"objects=%@", objects);
    
    // 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"];
    NSLog(@"objects=%@", objects);


  #pragma mark 遍历字典
  NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"v1", @"k1",
                          @"v2", @"k2",
                          @"v3", @"k3", nil];
    // 遍历字典的所有key
    for (id key in dict) {
        id value = [dict objectForKey:key];
        NSLog(@"%@=%@", key, value);
    }


 NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"v1", @"k1",
                          @"v2", @"k2",
                          @"v3", @"k3", nil];
    // key迭代器
    NSEnumerator *enumer = [dict keyEnumerator];
    id key = nil;
    while ( key = [enumer nextObject]) {
        id value = [dict objectForKey:key];
        NSLog(@"%@=%@", key, value);
    }
    
      // 对象迭代器
    // [dict objectEnumerator];



//block
 NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"v1", @"k1",
                          @"v2", @"k2",
                          @"v3", @"k3", nil];
    [dict enumerateKeysAndObjectsUsingBlock:
     ^(id key, id obj, BOOL *stop) {
        NSLog(@"%@=%@", key, obj);
    }];