ios – 在目标C中序列化异步任务

>发出网络请求
>显示UIAlertView

这通常是一项棘手的业务,大多数串行队列样本在NSBlockOperation的块中显示“睡眠”.这不起作用,因为只有在回调发生时才完成操作.

我已经通过继承NSOperation实现了这个,这是实现中最有趣的部分：

+ (MYOperation *)operationWithBlock:(CompleteBlock)block
{
    MYOperation *operation = [[MYOperation alloc] init];
    operation.block = block;
    return operation;
}

- (void)start
{
    [self willChangeValueForKey:@"isExecuTing"];
    self.execuTing = YES;
    [self didChangeValueForKey:@"isExecuTing"];
    if (self.block) {
        self.block(self);
    }
}

- (void)finish
{
    [self willChangeValueForKey:@"isExecuTing"];
    [self willChangeValueForKey:@"isFinished"];
    self.execuTing = NO;
    self.finished = YES;
    [self didChangeValueForKey:@"isExecuTing"];
    [self didChangeValueForKey:@"isFinished"];
}

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

- (BOOL) isExecuTing
{
    return self.execuTing;
}

这很好用,这是一个示范……

NSOperationQueue *q = [[NSOperationQueue alloc] init];
q.maxConcurrentOperationCount = 1;

dispatch_queue_t queue = dispatch_queue_create("1",null);
dispatch_queue_t queue2 = dispatch_queue_create("2",null);

MYOperation *op = [MYOperation operationWithBlock:^(MYOperation *o) {
    NSLog(@"1...");
    dispatch_async(queue,^{
        [NSThread sleepForTimeInterval:2];
        NSLog(@"1");
        [o finish]; // this signals we're done
    });
}];

MYOperation *op2 = [MYOperation operationWithBlock:^(MYOperation *o) {
    NSLog(@"2...");
    dispatch_async(queue2,^{
        [NSThread sleepForTimeInterval:2];
        NSLog(@"2");
        [o finish]; // this signals we're done
    });
}];

[q addoperations:@[op,op2] waitUntilFinished:YES];

[NSThread sleepForTimeInterval:5];

注意,我也使用了睡眠,但确保这些是在@L_489_4@线程中执行以模拟网络调用.日志内容如下

1...
1
2...
2

这是所希望的.这种方法有什么问题？有什么警告我应该知道吗？