如何在延迟和后台线程中调用方法

Question

我有一个方法,我想在后面-viewDidLoad和后台线程中调用.有没有办法结合这两种方法:

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

和

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

Answer 1

Grand Central Dispatch dispatch_after()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);

Answer 2

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)]
});

代码未经测试

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
    });
}