在执行之间暂停执行一个接一个的方法 [英] Executing methods one after another with pauses between executing

问题描述

新手obj-c问题。
我正在为Appstore写一个简单的iPad演示文稿。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。主结构如下所示：

Newbie obj-c question. I am writing a simple iPad presentation not for Appstore. My task is to implement few methods executed one after another with little pauses between them. Main structure looks like this:

• 查看加载


• 暂停两秒钟，然后执行method1


• 暂停两秒钟，然后执行method2


• 暂停两秒钟，然后执行method3
  等......

• view loads
• two seconds pause, then executing method1
• two seconds pause, then executing method2
• two seconds pause, then executing method3 etc...

我从-viewDidLoad调用的第一个方法：

First method I am calling from -viewDidLoad:

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

此处一切正常，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：

Everything is ok here, method starts 2 seconds after view loads. From inside method1 I try to call method 2 in the same way but it start to execute simultaneously with method1. Same way triggered method3 (called from method2) and all methods after them not executed at all. I tried to situate all this methods in -ViewDidLoad and to call them with delays:

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

但是在method2调用之后所有方法都没有执行。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？或者也许是其他问题？

But after method2 is calling all methods after didn't executed. If I understand right the issue in threads. Do I need to use GCD to execute methods in different queues? Or maybe problem in else?

谢谢，同事们！

推荐答案

您可以将这些添加到NSOperation队列...

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];
}];

...

然后只会在之前的每一个上运行一个已经完成，并为你提供了2秒的延迟。

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

小心使用它来做一个UI的东西。这将在后台线程中运行，因此您可能需要处理它。

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.

也许这可能会更好，你可以通过继承NSOperation来做到这一点，但这是很多工作没有多大好处。

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

从你想要的地方运行这个，我建议将所有这些放入一个名为setUpQueue的函数中。

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

然后从viewWillAppear或viewDidLoad或其他地方，按下按钮等...执行...

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

[self setUpQueue];

所有你需要做的就是在队列中添加东西，队列将自行管理。

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

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