iphone - NSOperation 中的异步方法

Question

我正在从 Facebook Connect 获取一些数据(使用 FBConnect Objective-C 2.0 框架)，并且我在 NSOperation 中完成所有这些操作。它位于 NSOperation 中，因为我还运行了其他几个操作，这就是其中之一。

问题在于所有 FBConnect 调用都是异步的。因此，NSOperation 的 main 方法很快完成，并且该操作被标记为已完成。

有什么办法可以克服这个问题吗？ FBConnect 中似乎没有同步选项!

非常感谢，

迈克

Answer 1

下面是一个完整的示例。在您的子类中，异步方法完成后，调用 [selfcompleteOperation] 转换到完成状态。

@interface AsynchronousOperation()
// 'executing' and 'finished' exist in NSOperation, but are readonly
@property (atomic, assign) BOOL _executing;
@property (atomic, assign) BOOL _finished;
@end

@implementation AsynchronousOperation

- (void) start;
{
    if ([self isCancelled])
    {
        // Move the operation to the finished state if it is canceled.
        [self willChangeValueForKey:@"isFinished"];
        self._finished = YES;
        [self didChangeValueForKey:@"isFinished"];
        return;
    }

    // If the operation is not canceled, begin executing the task.
    [self willChangeValueForKey:@"isExecuting"];
    [NSThread detachNewThreadSelector:@selector(main) toTarget:self withObject:nil];
    self._executing = YES;
    [self didChangeValueForKey:@"isExecuting"];

}

- (void) main;
{
    if ([self isCancelled]) {
        return;
    }

}

- (BOOL) isAsynchronous;
{
    return YES;
}

- (BOOL)isExecuting {
    return self._executing;
}

- (BOOL)isFinished {
    return self._finished;
}

- (void)completeOperation {
    [self willChangeValueForKey:@"isFinished"];
    [self willChangeValueForKey:@"isExecuting"];

    self._executing = NO;
    self._finished = YES;

    [self didChangeValueForKey:@"isExecuting"];
    [self didChangeValueForKey:@"isFinished"];
}

@end