xcode 在主线程上调用 dispatch_sync(dispatch_get_global_queue()) 会导致应用程序“挂起”吗？
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Does calling dispatch_sync(dispatch_get_global_queue()) on main thread cause app to "hang"?
提问by FlowUI. SimpleUITesting.com
// Method called when a button is clicked
- (void)handleClickEvent {
dispatch_sync(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self backgroundProcessing];
});
// Some code to update the UI of the view
....
[self updateUI];
....
}
1) handleClickEvent is called on the main thread when a button on the view is pressed.
1）当按下视图上的按钮时，在主线程上调用handleClickEvent。
2) I used dispatch_sync() because the following code that updates the UI of the view cannot be done until a variable in the backgroundProcessing method is calculated.
2）我使用dispatch_sync()是因为在backgroundProcessing方法中的一个变量被计算之前，下面的更新视图UI的代码无法完成。
3) I used dispatch_get_global_queue in order to get the backgroundProcessing off the main thread. (following the rule: generally put background processing off main thread and generally put code that affect the UI on the main thread).
3）我使用 dispatch_get_global_queue 来从主线程中获取 backgroundProcessing。（遵循规则：一般将后台处理放在主线程之外，一般将影响UI的代码放在主线程上）。
My question is: Does the backgroundProcessing method "hang" the main thread until it is complete since I am using dispatch_sync?
我的问题是：自从我使用 dispatch_sync 以来，backgroundProcessing 方法是否“挂起”主线程直到它完成？
EDIT:Based on the answer below i have implemented this solution:
编辑：基于下面的答案，我已经实现了这个解决方案：
- (void)handleClickEvent {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self backgroundProcessing];
dispatch_async(dispatch_get_main_queue(), ^{
[self updateUI];
});
});
}
solution from this link: Completion Callbaks
来自此链接的解决方案：Completion Callbaks
回答by Gary
Yes, dispatch_sync will block until the task is complete. Use dispatch_async and when the job is complete have it post a block back to the main queue to update the view.
是的，dispatch_sync 会阻塞直到任务完成。使用 dispatch_async 并在作业完成后将块发布回主队列以更新视图。
