Objective C: App freezes when using a timer

It took me ho开发者_如何学JAVAurs to figure out how to implement a timer into my program, but when it runs, the app doesn't load completely as it did before the timer.

In my main.m:

int main (int argc, const char * argv[]) {  
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

 OutLauncher *theLauncher = [[OutLauncher alloc] init];
NSTimer *theTimer = [theLauncher getTimer];
[theTimer retain];
[[NSRunLoop currentRunLoop] addTimer: theTimer forMode: NSDefaultRunLoopMode];

 [[NSRunLoop currentRunLoop] run];

 [pool release];
 return 0;  
 }

The file OutLauncher is being imported into that, which looks like this:

- (void)doStuff {  
NSLog( @"Doing Stuff");  

}

 - (NSTimer *)getTimer{  
 NSTimer *theTimer;

 theTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector: @selector(doStuff) userInfo:nil repeats:YES];

 return [theTimer autorelease];
}

The timer works, the console updates every second with the phrase "doing stuff" but the rest of the program just won't load. It will if I comment out the code I added to int main though

A few things:

You don't need to autorelease the timer you return after setting one up with [NSTimer scheduledTimerWithTimeInterval:] It is already autoreleased.

The timer created via scheduledTimerWithInterval is already added to the default run loop. So you don't need to use the following:

[[NSRunLoop currentRunLoop] addTimer: theTimer forMode: NSDefaultRunLoopMode];
[[NSRunLoop currentRunLoop] run];

In fact, you don't even need to keep a reference to the timer unless you need to cancel it yourself.

Here is what apple has to say about what you are doing in the documentation

run

Puts the receiver into a permanent loop, during which time it processes data from all attached input sources.

• (void)run Discussion If no input sources or timers are attached to the run loop, this method exits immediately; otherwise, it runs the receiver in the NSDefaultRunLoopMode by repeatedly invoking runMode:beforeDate:. In other words, this method effectively begins an infinite loop that processes data from the run loop’s input sources and timers.

Manually removing all known input sources and timers from the run loop is not a guarantee that the run loop will exit. Mac OS X can install and remove additional input sources as needed to process requests targeted at the receiver’s thread. Those sources could therefore prevent the run loop from exiting.

If you want the run loop to terminate, you shouldn't use this method. Instead, use one of the other run methods and also check other arbitrary conditions of your own, in a loop. A simple example would be:

BOOL shouldKeepRunning = YES;
// global NSRunLoop *theRL = [NSRunLoop currentRunLoop]; while (shouldKeepRunning && [theRL runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]); where shouldKeepRunning is set to NO somewhere else in the program.

Availability Available in iOS 2.0 and later.

So it looks like your code is doing what it is supposed to do. It is Logging all the timer events and waiting indefinitely for the run loop.

It looks like you're making it a lot more complicated than it needs to be. You don't need to put any code in your main.m file. If you want to fire the doStuff method every second, this is all the code you need:

NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector: @selector(doStuff) userInfo:nil repeats:YES];

You don't need to (auto)release it yourself. timer is already autoreleased. If you want to be able to cancel the timer, you will need to keep a reference of it. Then when you want to cancel, you just call invalidate and set the reference to nil.