爲什麼我的財產不被釋放？

Question

我有一個lazily加載的屬性定義如下，似乎每次我像foo.bar訪問它時保留。在'for'循環退出（從init調度異步）後，bar的所有副本都會被釋放，但同時它們都會建立起來，並且會收到內存警告。

這是怎麼發生的？ ARC是否從未在內部清除未使用的內存？或者我在某種程度上導致了我的調度或在一個塊中的保留週期？

@interface Foo : NSObject 

@property (nonatomic, strong) MyAlgorithm *bar; 

@end 

@implementation Foo 

- (id)init { 

    if (self = [super init]) { 

    __weak Foo *weakSelf = self; 

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ 

     weakSelf.testAudioFilePaths = [[NSBundle mainBundle] pathsForResourcesOfType:kAudioFileWavType inDirectory:kTestFilesDirectory]; 

     for (NSString *path in weakSelf.testAudioFilePaths) { 

      weakSelf.bar = nil; // this is so we rebuild it for each new path 

      [weakSelf readDataFromAudioFileAtPath:path]; 

     } 

    }); 
    } 
    return self; 
} 

- (MyAlgorithm *)bar { 
    if (!_bar) { 
     _bar = [[MyAlgorithm alloc] initWithBar:kSomeBarConst]; 
    } 
    return _bar; 
} 


@end 

Answer 1

答案是@autoreleasepool塊上的循環內包裹代碼位，所以，游泳池循環的每次迭代後倒掉，而不是在循環退出後未來的某個時刻：

- (id)init { 

    if (self = [super init]) { 

    __weak Foo *weakSelf = self; 

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ 

     weakSelf.testAudioFilePaths = [[NSBundle mainBundle] pathsForResourcesOfType:kAudioFileWavType inDirectory:kTestFilesDirectory]; 

     for (NSString *path in weakSelf.testAudioFilePaths) { 

      @autoreleasepool { 

       weakSelf.bar = nil; // this is so we rebuild it for each new path 

       [weakSelf readDataFromAudioFileAtPath:path]; 
      } 

     } 

    }); 
    } 
    return self; 
}