objective-c - 为什么 waitUntilAllOperationsAreFinished 不在此代码中等待？

Question

-(NSInteger) buttonIndexWithMessage:(NSString *) title andArrayOfOptions:(NSArray *) options
{
    self.operation=[NSOperationQueue new];

    [self.operation addOperationWithBlock:^{
        [[NSOperationQueue mainQueue]addOperationWithBlock:^{
            UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:title
                                                                     delegate:self
                                                            cancelButtonTitle:nil
                                                       destructiveButtonTitle:nil
                                                            otherButtonTitles:nil];

            for (NSString * strOption in options) {
                [actionSheet addButtonWithTitle:strOption];
            }

            [actionSheet showInView:[BGMDApplicationsPointers window]];
        }];
        self.operation.suspended=true; //Okay make t
    }];

    [self.operation waitUntilAllOperationsAreFinished];//Don't get out of the function till user act.

    //Wait till delegate is called.
    return self.buttonIndex;//I want to return buttonIndex here.
}

即使self.operation还没有结束，执行点一直移动直到返回self.buttonIndex。

Answer 1

你怎么知道 self.operation 没有完成？您添加到其中的操作执行起来非常快:它只是将另一个操作添加到主队列。

你好像认为行

self.operation.suspended=true;

应该阻止正在进行的操作。但是来自 documentation :

This method suspends or resumes the execution of operations. Suspending a queue prevents that queue from starting additional operations. In other words, operations that are in the queue (or added to the queue later) and are not yet executing are prevented from starting until the queue is resumed. Suspending a queue does not stop operations that are already running.

您的操作已经在运行，因此不受影响。

为什么不告诉我们您实际想要实现的目标，我们可以建议实现目标的好方法。