检测代码是否在 Objective-C 的主线程上运行的正确方法是什么？(iOS)
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What is the proper way to detect if code is running on the main thread in Objective-C? (iOS)
提问by Cameron Hotchkies
My code needs to guarantee a certain operation run on the main thread, but calls may come from background threads.
我的代码需要保证某个操作在主线程上运行，但调用可能来自后台线程。
To detect situations in the background I was using the following:
为了检测背景中的情况，我使用了以下内容：
- (void)selectorToRunInMainThread:(id)arguments
{
// push to main thread
if ([NSRunLoop currentRunLoop] != [NSRunLoop mainRunLoop])
{
[self performSelectorOnMainThread:@selector(selectorToRunInMainThread:) withObject:arguments waitUntilDone:NO];
return;
}
/*
... function content ...
*/
}
This works on iOS 4 and iOS 3.2 but not on iOS 3.1.3 and earlier. In these earlier versions, the function will keep getting called in an endless loop.
这适用于 iOS 4 和 iOS 3.2，但不适用于 iOS 3.1.3 及更早版本。在这些早期版本中，该函数将在无限循环中不断被调用。
Changing the comparison to:
将比较更改为：
if (![[NSRunLoop currentRunLoop] isEqualTo:[NSRunLoop mainRunLoop]])
if (![[NSRunLoop currentRunLoop] isEqualTo:[NSRunLoop mainRunLoop]])
has no effect, they still never compare to the same value.
没有效果，它们仍然永远不会与相同的值进行比较。
I found a solution that appears to be working, but I'd like to see what other people suggest first.
我找到了一个似乎有效的解决方案，但我想先看看其他人的建议。
回答by bbum
[NSThread isMainThread]and, if not, dispatch via any of a number of mechanisms to the main thread (what you have is fine).
[NSThread isMainThread]并且，如果没有，则通过多种机制中的任何一种调度到主线程（您所拥有的都很好）。
