如何在延迟和后台线程中调用方法

I have a method what I want to call after -viewDidLoad and in background thread. Is there way to combine this two methods:

我有一个方法，我想在-viewDidLoad和后台线程后调用。有没有办法结合这两种方法：

[self performSelector:(SEL) withObject:(id) afterDelay:(NSTimeInterval)]

[self performSelector：（SEL）withObject：（id）afterDelay：（NSTimeInterval）]

and

和

[self performSelectorInBackground:(SEL) withObject:(id)]?

[self performSelectorInBackground：（SEL）withObject：（id）]？

4 个解决方案

#1

Grand Central Dispatch has dispatch_after() which will execute a block after a specified time on a specified queue. If you create a background queue, you will have the functionality you desire.

Grand Central Dispatch有dispatch_after（），它将在指定队列上的指定时间后执行一个块。如果您创建后台队列，您将拥有所需的功能。

dispatch_queue_t myBackgroundQ = dispatch_queue_create("com.romanHouse.backgroundDelay", NULL);
// Could also get a global queue; in this case, don't release it below.
dispatch_time_t delay = dispatch_time(DISPATCH_TIME_NOW, seconds * NSEC_PER_SEC);
dispatch_after(delay, myBackgroundQ, ^(void){
    [self delayedMethodWithObject:someObject];
});
dispatch_release(myBackgroundQ);

#2

Try the following:

请尝试以下方法：

// Run in the background, on the default priority queue
dispatch_async( dispatch_get_global_queue(0, 0), ^{
    [self performSelector:(SEL) withObject:(id) afterDelay:(NSTimeInterval)]
});

Code not tested

代码未经测试

Be aware that your selector/method must not use UIKit (so don't update the UI) or access UIKit properties (like frame) so your selector may need to kick off work back to the main thread. e.g.

请注意，您的选择器/方法不能使用UIKit（因此不要更新UI）或访问UIKit属性（如框架），因此您的选择器可能需要将工作重新启动回主线程。例如

(id)SomeMethod:UsingParams: {

    // Do some work but the results

    // Run in the background, on the main queue
    dispatch_async(dispatch_get_main_queue(), ^{
        // Do something UIKit related
    });
}

#3

[self performSelector:(SEL) withObject:(id) afterDelay:(NSTimeInterval)]

Performs a selector on the thread that it is being called. So when you call it from a background thread it will run there...

在正在调用它的线程上执行选择器。所以当你从后台线程调用它时它会在那里运行...

#4

You can do that per example:

你可以按照例子做到这一点：

dispatch_time_t delay = dispatch_time( DISPATCH_TIME_NOW, <delay in seconds> * NSEC_PER_SEC );
dispatch_after( delay, dispatch_get_main_queue(), ^{
    [self performSelectorInBackground: <sel> withObject: <obj>]
});

Somehow a mixed solution. It would be better to stick with a full GCD approach tho.

不知何故，混合解决方案。坚持完整的GCD方法会更好。

#1