在哪个线程中调用iOS完成处理程序块？ [英] In which thread are iOS completion handler blocks called?

问题描述

例如，在 GKScore 的 reportScoreWithCompletionHandler （文档），假设你调用

For example, in GKScore's reportScoreWithCompletionHandler (documentation), suppose you call

[score reportScoreWithCompletionHandler:^(NSError *error) {
   // do some stuff that may be thread-unsafe
}];

在哪个线程中调用完成处理程序：主线程，与<$ c相同的线程$ c> reportScoreWithCompletionHandler 被调用，或者是一个不同的线程（可能是实际得分报告的线程）？

In which thread will the completion handler be called: the main thread, the same thread as reportScoreWithCompletionHandler was called, or a different thread (presumably the thread that the actual score reporting is done)?

换句话说，在完成处理程序中完成的工作是否需要是线程安全的（例如，它在什么线程中完成并不重要）？

In other words, does the work done in the completion handler need to be thread-safe (as in, it doesn't matter what thread it's done in)?

推荐答案

实际上并不重要。

如果你需要在主线程中运行你的完成，只需将它发送到主线程：

If you need your completion to run in the main thread, just dispatch it to the main thread:

[score reportScoreWithCompletionHandler:^(NSError *error) {
    dispatch_async(dispatch_get_main_queue(), ^{
        // do your stuff here
    });
}];

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