objective-c - PFObject 如何允许像 NSMutableDictionary 这样的下标？

Question

我正在阅读 Parse 的 iOS 开发人员指南。 我对它显示 PFObject 使用下标语法分配给键感到困惑。

PFObject *gameScore = [PFObject objectWithClassName:@"GameScore"];
gameScore[@"score"] = @1337;
gameScore[@"playerName"] = @"Sean Plott";
gameScore[@"cheatMode"] = @NO;


PFObject *gameScore = [PFObject objectWithClassName:@"GameScore"];
gameScore[@"score"] = @1337;

首先我认为 PFObject 一定是扩展了 NSMutableDictionary，但是 PFObject 只是扩展了 NSObject。它如何表现得像 NSMutableDictionary？

我如何为我自己的类(class)做这件事？

Answer 1

NSHipster有答案:

Similarly, custom-keyed subscripting can be added to your class by declaring and implementing these methods:

- (id)objectForKeyedSubscript:(*KeyType*)key;
- (void)setObject:(id)obj forKeyedSubscript:(*KeyType*)key;