iOS Objective C覆蓋屬性設置器

Question

在課堂上，我有@property BOOL clearCookies;

我想進行設置，以便在設置項目時可以做一些其他事情。

在我的代碼中，我可以做類似classInstance.clearCookies = YES;

然后在setter方法中，類似於android中的以下Java示例：

public void setClearCookies(boolean clearCookies) {
        _instance.clearCookies = clearCookies;
        _instance.doOtherThings();
    }

在目標C中實現此目標的最佳方法是什么？ 基本上，我想設置boolean屬性，然后再做一些其他事情（實際上是從UIWebView清除cookie）

Answer 1

您可以這樣：

-(void)setClearCookies:(BOOL)clearCookies {
        _clearCookies = clearCookies;
       [self doOtherThings];
    }

Answer 2

-(void)setClearCookies:(BOOL)clearCookies
{
    @synchronized(self)
    {
       _clearCookies = clearCookies;
       [self doOtherThings];
   } 
}

- (BOOL)clearCookies
{
   @synchronized (self)
   {
       return _clearCookies;
   }
}

Answer 3

避免線程沖突的另一種方法（ @synchronized()替代方法）是使用Grand Central Dispatch（在大多數情況下，它比前者快 ）：

@property (assign, nonatomic) BOOL clearCookies;

// Later in code
static dispatch_queue_t clearCookiesQueue;

- (void)setClearCookies:(BOOL)clearCookies {
    [self initializeClearCookiesQueue];

    dispatch_async(clearCookiesQueue, ^{ // Note, this is "async"
        _clearCookies = clearCookies;
    });
}


- (BOOL)clearCookies {
    [self initializeClearCookiesQueue];

    __block BOOL clearCookies;
    dispatch_sync(clearCookiesQueue, ^{ // Note, this is "sync"
        clearCookies = _clearCookies;
    });

    // As "sync" waits until the operation is finished, you can define
    // your other operations here safely.
    [self doOtherStuff];

    return clearCookies;
}


/**
    Checks if the queue for the clearCookies property is initialized and,
    if it's not, initializes it.
*/
- (void)initializeClearCookiesQueue {
    if ( ! clearCookiesQueue ) {
        // We'll use a serial queue to avoid conflicts reading/writing the ivar
        clearCookiesQueue = dispatch_queue_create("com.yourapp.yourviewcontroller.someUniqueIdentifier", DISPATCH_QUEUE_SERIAL); // Note, this is a C string, not NSString
    }
}

如果您不關心線程，或者不需要線程，那么只需覆蓋您的setter就可以了：

- (void)setClearCookies:(BOOL)clearCookies {
    _clearCookies = clearCookies;
    [self doOtherStuff];
}