cocoa-touch - 为什么我的 NSOperation 子类永远不会完成？

Question

我有一个 NSOperation我想同时运行的子类。

我的理解是，要使并发操作起作用:

我需要定义 isConcurrent返回 YES .

我需要定义 start方法

我需要为 isExecuting 发送 KVO 通知和 isFinished完成后。

使用 @synthesize当 isExecuting 的值达到时，将自动发送适当的 KVO 通知和 isFinished被改变。

尽管如此，我已经确认我的队列永远不会移动到下一个项目。

这是我的代码的主要内容:

@interface MyOperation()

@property (readwrite) BOOL isExecuting;
@property (readwrite) BOOL isFinished;

@end

@implementation MyOperation

- (void)start
{
    @autoreleasepool {
        self.isExecuting = YES;
        self.HTTPOperation = [[AFHTTPRequestOperation alloc] initWithRequest: URLRequest];

        _HTTPOperation.completionBlock = [^{
            [self completed];

            self.isExecuting = NO;
            self.isFinished = YES;
        } copy];

        [_HTTPOperation start];
    }
}

- (BOOL)isConcurrent
{
    return YES;
}

- (void)completed
{
}

@end

我错过了什么？

(这是在 iPhone 上，但我无法想象这很重要。)

Answer 1

看起来像任何 KVO 通知 @synthesize发送不够 NSOperationQueue继续前进。

手动发送通知可以解决问题:

- (void)start
{
    @autoreleasepool {
        [self willChangeValueForKey:@"isExecuting"];
        self.isExecuting = YES;
        [self didChangeValueForKey:@"isExecuting"];

        NSURLRequest *URLRequest = [self buildRequest];
        if (!URLRequest) {
            [self willChangeValueForKey:@"isFinished"];
            [self willChangeValueForKey:@"isExecuting"];
            _isExecuting = NO;
            _isFinished = YES;
            [self didChangeValueForKey:@"isExecuting"];
            [self didChangeValueForKey:@"isFinished"];
            return;
        }

        self.HTTPOperation = [[AFHTTPRequestOperation alloc] initWithRequest: URLRequest];

        _HTTPOperation.completionBlock = [^{
            [self completed];

            [self willChangeValueForKey:@"isFinished"];
            [self willChangeValueForKey:@"isExecuting"];
            _isExecuting = NO;
            _isFinished = YES;
            [self didChangeValueForKey:@"isExecuting"];
            [self didChangeValueForKey:@"isFinished"];
        } copy];

        [_HTTPOperation start];
    }
}

也可以看看:

Why does NSOperation disable automatic key-value observing?