如何調用延遲和後臺線程的方法

Question

我有一個方法，我想在-viewDidLoad和後臺線程後調用。有沒有辦法這兩種方法相結合：

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

和

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

Answer 1

Grand Central Dispatch有dispatch_after()它將在指定隊列上的指定時間後執行一個塊。如果你創建一個背景隊列，你將擁有你想要的功能。

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

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

在被調用的線程上執行選擇器。所以當你從後臺線程調用它時，它將在那裏運行...

Answer 3

你可以做到每例如：

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>] 
}); 

莫名其妙的混合溶液。最好堅持一個完整的GCD方法。

Answer 4

嘗試以下操作：

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

代碼沒有測試

請注意，您的選擇/方法不能使用UIKit的（所以不要更新UI）或訪問UIKit的特性（如幀）所以你的選擇器可能需要開始工作回主線程。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 
    }); 
}