在执行之间暂停执行一个接一个的方法

Question

新手obj-c问题.我正在写一个简单的iPad演示文稿而不是Appstore.我的任务是实现一个接一个地执行的几个方法,它们之间几乎没有暂停.主要结构如下:

• 查看负载
• 两秒钟暂停,然后执行method1
• 两秒钟暂停,然后执行method2
• 两秒钟暂停,然后执行method3等...

我从-viewDidLoad调用的第一个方法:

NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(firstCountStarts) userInfo:nil repeats:NO];

一切都很好,方法在视图加载后2秒开始.从method1里面我尝试以相同的方式调用方法2,但它开始与method1同时执行.同样的方法触发了method3(从method2调用)以及它们之后根本没有执行的所有方法.我试图将所有这些方法放在-ViewDidLoad中,并用延迟来调用它们:

 [self method1];
 [self performSelector:@selector(method2) withObject:nil afterDelay:2];
 [self performSelector:@selector(method3) withObject:nil afterDelay:4];
 etc...

但是在method2调用所有方法之后没有执行.如果我理解线程中的问题.我是否需要使用GCD在不同的队列中执行方法？或者可能是其他问题？

谢谢,同事们!

Answer 1

You could add these to an NSOperation queue...

NSOperationQueue *queue = [NSOperationQueue new];

queue.maxConcurrentOperationCount = 1;

[queue  addOperationWithBlock:^{
    [self method1];
}];

[queue  addOperationWithBlock:^{
    [NSThread sleepForTimeInterval:2.0];
    [self method2];
}];

[queue  addOperationWithBlock:^{
    [NSThread sleepForTimeInterval:2.0];
    [self method3];
}];

...

This will then run each one only after the previous one has finished and put the 2 second delay in for you.

Careful about using this to do an UI stuff though. This will run in a Background thread so you may need to deal with that.

Maybe this might work better you could do it by subclassing NSOperation but that's a lot of work for not much benefit.

Run this from where ever you want, I suggest putting all this into a function called setUpQueue or something.

Then from viewWillAppear or viewDidLoad or somewhere else, on a button press, etc... do...

[self setUpQueue];

All you have to do is add stuff to the queue, the queue will then manage itself.