我應該在這裏設置__block變量爲零，爲什麼？

Question

這是Why do we have to set __block variable to nil?

基本上都採用塊可引起ARC保留週期，我還是不明白，爲什麼

http://developer.apple.com/library/mac/#releasenotes/ObjectiveC/RN-TransitioningToARC/Introduction/Introduction.html#//apple_ref/doc/uid/TP40011226-CH1-SW11

-(void)getReviewAndView{ 
    if(![[GrabClass grab] cekInet]){return;} 
    CM(@"get review and view"); 
    self.viewlbl.text=@"0 view"; 
    self.reviewlbl.text=@"0 review"; 

    Business * businessReviewed = [BNUtilitiesQuick currentBusiness]; 

    NSString *alamat=[NSString stringWithFormat:@"http://...",businessReviewed.ID]; 

    CLog(@"alamat:%@", alamat); 

    __block NSDictionary * dic = nil; 


    [Tools doBackground:^{ 
     dic=(NSDictionary *)[GrabClass JsonParser:alamat]; //dic get set here 
     [Tools doForeGround:^{ 
      NSString *countView= [[dic objectForKey:businessReviewed.ID] objectForKey:@"CountViews"]; 

      CLog(@"countView:%@", countView); 
      NSString *countReview=[[dic objectForKey:businessReviewed.ID] objectForKey:@"Review"]; //dic get used here 
      NSString * reviews=@"review"; 
      NSString * view=@"view"; 


      //blablabla 

      self.viewlbl.text=[NSString stringWithFormat:@"%@ %@",countView,view ]; 
      self.reviewlbl.text=[NSString stringWithFormat:@"%@ %@",countReview,reviews]; 
      dic =nil; //should this be called? What happen if it doesn't? 
     }]; 
    }]; 
} 

Answer 1

如果你不知道，如果延續你有一個保留週期或沒有，你應該在儀器的「泄漏」工具下運行你的代碼，它會告訴你任何泄漏或保留週期。

另請注意，在最新版本的Xcode中，如果您創建這些父/塊週期中的一個，編譯器將爲您生成警告。

在你的情況下，你大概不需要擔心。 dic不保留引用它的塊，所以這裏沒有循環。但最好的檢查方法是使用泄漏/分配工具。