objective-c - 是否可以将 "keyed-subscripting"添加到 Class 对象？

Question

在......的脉络中

@implementation MyClass
- (id) objectForKeyedSubscript:(id)k { 
       return [self something:k]; 
}

是否也可以“下标”Class 对象？我也将要和你一起找出答案......但我想我会在测试时发布这个问题，我自己......

+ (id) objectForKeyedSubscript:(id)k { 
       return [self.shared something:k]; 
}

唉..它不是...

id x = MyClass[@"document"];

error: unexpected interface name 'MyClass': expected expression

但为什么，爸爸？ Class' sure get the short end NSObject 的棍子，如果你问我的话。

Answer 1

Josh Caswell's comment指出问题:

You're using the type name. Try it with a class object in a variable. id myClass = [MyClass class]; myClass[@"document"]; Or [MyClass class][@"document"]

我发誓我已经尝试过了。 圣经。但证据就在布丁中......

@interface MyClass : NSObject
@property (readonly) id  boring;
@end
@implementation MyClass
- boring   { return @"typical"; }
+ document { return  @"YEEHAW"; }
- objectForKeyedSubscript:key { return [self valueForKey:key]; }
+ objectForKeyedSubscript:key { 
  return [self performSelector:NSSelectorFromString(key)]; 
}
@end

...

id a = MyClass.new;
id x = a[@"boring"];   // "typical" (via "normal" keyed subscription)
id b = MyClass.class;
   x = z[@"document"]; // "YEEHAW" (via CLASS keyed-subscript!)

或者我所有的单行freaky-deaky's 在那里...

x = ((id)MyClass.class)[@"document"] // "YEEHAW"