Question

在课堂上我有@property BOOL clearCookies;

我想设置它，以便在设置项目时我可以做一些额外的事情。

在我的代码中，我可以执行classInstance.clearCookies = YES;

之类的操作

然后在setter方法中，像android这样的java示例：

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

在Objective C中实现这一目标的最佳方法是什么？基本上我想设置布尔属性，但是还要做其他一些事情（实际上是从UIWebView清除cookie）

Answer 1

你可以这样做：

-(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

避免线程冲突（替代@synchronized()）的另一种方法是使用Grand Central Dispatch（在大多数情况下比前者faster）：

@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
    }
}

如果您不关心线程，或者您不需要线程，只需覆盖您的setter即可：

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

iOS Objective C覆盖属性设置器

3 个答案: