嵌套 NSDictionary 的访问对象

Question

有没有办法在 Objective-C 中直接访问外部字典的内部字典？例如，我有一个对象的键，它是内部字典的一部分，有没有办法直接从该键访问对象。

GameDictionary {
  Indoor_Game = { "game1" = chess; "game2" = video_Game; "game3" = poker; };
  OutDoor_Game = { "game4" = cricket; "game5" = hockey; "game6" = football; };
};

我有一个键“game4”，但我不知道这个键的哪个字典对象存在，目前我必须在每个字典中搜索对象，我使用的代码是：

NSString* gameName = nil;
NSString* gameKey = @"game4";
NSArray* gameKeys = [GameDictionary allKeys];
for (int index = 0; index < [gameKeys count]; index ++) {
  NSDictionary* GameType = [GameDictionary objectForKey:[gameKeys objectAtIndex:index]];
  if ([GameType objectForKey:gameKey]) {
    gameName = [GameType objectForKey:gameKey];
    break;
  }
}

他们有什么简单的方法可以直接访问内部字典而不是 for 循环。

Answer 1

valueForKeyPath 看起来像你想要的。

[GameDictionary valueForKeyPath:@"OutDoor_Game"]
//would return a dictionary of the games - "game4" = cricket; "game5" = hockey; "game6" = football;

[GameDictionary valueForKeyPath:@"OutDoor_Game.game4"]
//would return cricket

https://developer.apple.com/library/ios/DOCUMENTATION/Cocoa/Conceptual/KeyValueCoding/Articles/CollectionOperators.html