Simple question: what happens if I do this:
简单的问题:如果我这样做会发生什么:
- (void)viewDidLoad
{
[self performSelectorInBackground:@selector(myBGMethod) withObject:nil];
}
-(void)myBGMethod
{
[self myOtherMethod];
}
-(void)myOtherMethod
{
NSLog(@"This is not Inception");
//some more code here
}
Will the NSLog() and other code in myOtherMethod be run on the main thread or in the background?
myOtherMethod中的NSLog()和其他代码是在主线程还是在后台运行?
3 个解决方案
#1
1
It'll be run in the background thread.
它将在后台线程中运行。
You can confirm this by calling NSLog inside all your methods. By default, NSLog prints the thread number along the process ID (pid).
您可以通过在所有方法中调用NSLog来确认这一点。默认情况下,NSLog沿进程ID(pid)打印线程号。
#2
1
It'll be run in the background. Once you make the call to myBGMethod in another thread, whatever it calls is made on that same thread unless it specifically requests another thread.
它将在后台运行。一旦你在另一个线程中调用myBGMethod,它调用的是在同一个线程上进行的,除非它特意请求另一个线程。
As a side note, depending on which version of iOS you want to support, you might want to learn more about Grand Central Dispatch. It makes multithreading a lot simpler.
作为旁注,根据您要支持的iOS版本,您可能想要了解有关Grand Central Dispatch的更多信息。它使多线程变得更加简单。
#3
1
If you are ever curious about what thread a particular line of code is executing on, you can put a breakpoint on that line and check the Debug Navigator pane in Xcode:
如果您对某个特定代码行正在执行的线程感到好奇,可以在该行上放置一个断点并检查Xcode中的Debug Navigator窗格:
In this case, I put a breakpoint on NSLog(...)
在这种情况下,我在NSLog上放了一个断点(...)
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSLog(@"HI!");
});
and you can see that we're in Thread 2 com.apple.root.default-priority
你可以看到我们在线程2 com.apple.root.default-priority
#1
1
It'll be run in the background thread.
它将在后台线程中运行。
You can confirm this by calling NSLog inside all your methods. By default, NSLog prints the thread number along the process ID (pid).
您可以通过在所有方法中调用NSLog来确认这一点。默认情况下,NSLog沿进程ID(pid)打印线程号。
#2
1
It'll be run in the background. Once you make the call to myBGMethod in another thread, whatever it calls is made on that same thread unless it specifically requests another thread.
它将在后台运行。一旦你在另一个线程中调用myBGMethod,它调用的是在同一个线程上进行的,除非它特意请求另一个线程。
As a side note, depending on which version of iOS you want to support, you might want to learn more about Grand Central Dispatch. It makes multithreading a lot simpler.
作为旁注,根据您要支持的iOS版本,您可能想要了解有关Grand Central Dispatch的更多信息。它使多线程变得更加简单。
#3
1
If you are ever curious about what thread a particular line of code is executing on, you can put a breakpoint on that line and check the Debug Navigator pane in Xcode:
如果您对某个特定代码行正在执行的线程感到好奇,可以在该行上放置一个断点并检查Xcode中的Debug Navigator窗格:
In this case, I put a breakpoint on NSLog(...)
在这种情况下,我在NSLog上放了一个断点(...)
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSLog(@"HI!");
});
and you can see that we're in Thread 2 com.apple.root.default-priority
你可以看到我们在线程2 com.apple.root.default-priority