如何創建一個返回塊的objective-c方法

Question

-(NSMutableArray *)sortArrayByProminent:(NSArray *)arrayObject 
{ 
    NSArray * array = [arrayObject sortedArrayUsingComparator:^(id obj1, id obj2) { 
     Business * objj1=obj1; 
     Business * objj2=obj2; 
     NSUInteger prom1=[objj1 .prominent intValue]; 
     NSUInteger prom2=[objj2 .prominent intValue]; 
     if (prom1 > prom2) { 
      return NSOrderedAscending; 
     } 
     if (prom1 < prom2) { 
      return NSOrderedDescending; 
     } 
     return NSOrderedSame; 
    }]; 

    NSMutableArray *arrayHasBeenSorted = [NSMutableArray arrayWithArray:array]; 

    return arrayHasBeenSorted; 
} 

所以基本上我有這個塊，我用來排序數組。

現在我想寫一個返回該塊的方法。

我該怎麼做？

我試圖

+ (NSComparator)(^)(id obj1, id obj2) 
{ 
    (NSComparator)(^ block)(id obj1, id obj2) = {...} 
    return block; 
} 

這麼說吧，它尚不能工作。

Answer 1

方法簽名返回這樣的塊應該是

+(NSInteger (^)(id, id))comparitorBlock { 
    .... 
} 

這種分解：

+(NSInteger (^)(id, id))comparitorBlock; 
^^ ^ ^^ ^^  ^
ab c  d e e b  f 

a = Static Method 
b = Return type parenthesis for the method[just like +(void)...] 
c = Return type of the block 
d = Indicates this is a block (no need for block names, it's just a type, not an instance) 
e = Set of parameters, again no names needed 
f = Name of method to call to obtain said block 

更新：在你的特殊情況，NSComparator已經是塊型的。它的定義是：

typedef NSComparisonResult (^NSComparator)(id obj1, id obj2); 

因此，所有你需要做的就是返回此類型定義：

+ (NSComparator)comparator { 
    .... 
}