保留計數和removeFromSuperview

Question

我有一個UIView，當我初始化它已經保持數2，我不明白爲什麼，作爲一個結果，我不能removefromsuperview刪除它

ViewController.h

@property (nonatomic, retain)FinalAlgView * drawView; 

ViewController.m

self.drawView =[[FinalAlgView alloc]init]; 

NSLog(@"the retain count 1 of drawView is %d", [self.drawView retainCount]); 
//the retain count 1 of drawView is 2 

[self.bookReader addSubview:self.drawView]; 

NSLog(@"the retain count 2 of drawView is %d", [self.drawView retainCount]); 
//the retain count 2 of drawView is 3 

[self.drawView release]; 

NSLog(@"the retain count 3 of drawView is %d", [self.drawView retainCount]); 
//the retain count 3 of drawView is 2 

[UIView animateWithDuration:0.2 
       animations:^{self.drawView.alpha = 0.0;} 
       completion:^(BOOL finished){ [self.drawView removeFromSuperview]; 
       }]; 
//do not remove 

我不使用ARC

Answer 1

你canno t指望retainCount你會得到令人困惑的結果，最好不要使用它。

從Apple：

......這是非常不可能的，你可以從這個方法獲取有用的信息。

Answer 2

如null表示，不能依賴retainCount。假設你正在使用ARC，你的代碼實際上是編譯成這樣的事情：

FinalAlgView *dv = [[FinalAlgView alloc] init]; // Starts with retainCount of 1 
self.drawView = dv; // Increments the retainCount 

NSLog(@"the retain count 1 of drawView is %d", [self.drawView retainCount]); 
//the retain count 1 of drawView is 2 

... 
// do not remove 
... 
[dv release]; 

如果你不使用ARC，那麼你需要在你的第一行代碼改成這樣：

self.drawView =[[[FinalAlgView alloc]init]autorelease]; 

retainCount仍將從2開始，直到自動釋放池在runloop結束時耗盡。