将键添加到嵌套的NSDictionary

Question

我在为嵌套的NSDictionary创建新密钥时遇到问题.这就是我所做的

我有这种NSMutableDictionary

  NSMutableDictionary *Ga=[NSMutableDictionary dictionaryWithDictionary:@{@"Node1" :@{@"SubNode11" :@40,@"SubNode12":@30}}];

哪个NSLog为:

Node1 =     {
    SubNode11 = 40;
    SubNode12 = 30;
};

现在添加另一个根密钥和嵌套密钥我做了这个,

[Ga setObject:@{@"SubNode21" : @555} forKey:@"Node2"];

现在NSLog输出:

Node1 =     {
    SubNode11 = 40;
    SubNode12 = 30;
};
Node2 =     {
    SubNode21 = 555;
};
}

我需要向现有节点添加另一个密钥,比如SubNode22 = 345; 对于Node2在一个单独的代码行中,所以我认为这可能有效

[[Ga objectForKey:@"Node2"] setObject:@5555 forKey:@"SubNode22"];

但这显示错误"由于未捕获的异常终止应用程序'NSInvalidArgumentException',原因:' - [__ NSDictionaryI setObject:forKey:]:无法识别的选择器发送到实例"

我不知道问题是什么,这个方法对我来说似乎很直接..任何解决方案请.

Answer 1

这里的问题与嵌套无关.它与可变的诗歌不可变有关.如果字典不可变,则无法添加到字典中.

错误消息告诉你,NSDictionary没有调用setObject:ForKey:的方法,因为这是一种方法NSMutableDictionary.使用Apples新的文字词典@{ key: object}只能创建不可变的词典.

所以,你真正需要的是确保你创建NSMutableDictionaryS使用两种[NSMutableDictionary dictionaryWithObjectsAndKeys:];或[@{ Key: Object } mutableCopy]

所以这是你的代码改变了

NSMutableDictionary *subNode = [NSMutableDictionary dictionaryWithObjectsAndKeys:@40, @"SubNode11", @30, @"SubNode12", nil];
NSMutableDictionary *Ga = [NSMutableDictionary dictionaryWithObjectsAndKeys:subNode, @"Node 1", nil];
[Ga setObject:[NSMutableDictionary dictionaryWithObjectsAndKeys:@555, @"SubNode21", nil] forKey:@"Node2"];
[[Ga objectForKey:@"Node2"] setObject:@5555 forKey:@"SubNode22"];

您仍然可以使用一些新的下标功能.例如,您可以将代码更改为类似的内容,以便在执行相同操作时更具可读性:

NSMutableDictionary *Ga = [NSMutableDictionary dictionary];

// Create SubNodes
NSMutableDictionary *subNode1 = [NSMutableDictionary dictionary];
subNode1[@"SubNode11"] = @40;
subNode1[@"SubNode12"] = @30;

NSMutableDictionary *subNode2 = [NSMutableDictionary dictionary];
subNode2[@"SubNode21"] = @555;

// Set SubNodes to Main Node Container
Ga[@"Node1"] = subNode1;
Ga[@"Node2"] = subNode2;

// Set a nested subnode's value.
Ga[@"Node2"][@"SubNode22"] = @5555;