NSTimer does't work in CMD Project in xCode - objective-c

Question

I have problem with NSTimer in Objective-C. This is my source code:
Main.m
#import <Foundation/Foundation.h>
#import "TimerTest.h"
int main(int argc, const char * argv[]) {
#autoreleasepool {
TimerTest *timerTest = [[[TimerTest alloc] init] autorelease];
}
return 0;
}
TimerTest.h
#import <Foundation/Foundation.h>
#interface TimerTest : NSObject {
NSTimer *_timer;
}
#property (nonatomic, retain) NSTimer *timer;
- (id) init;
#end
TimerTest.m
#import "TimerTest.h"
#implementation TimerTest
#synthesize timer = _timer;
- (id) init {
if (self = [super init]) {
[NSTimer timerWithTimeInterval:0.5f
target:self
selector:#selector(tick:)
userInfo:nil
repeats:YES];
}
return self;
}
- (void) tick: (NSDate *) dt {
NSLog(#"Tick! \n");
}
- (void) dealloc {
self.timer = nil;
[super dealloc];
}
#end
My program should log "Tick! \n" every 0.5 second. But then my program is finished, xcode console is clear, that's meaning that NSLog in
-(void)tick:(NSDate *)dt method didn't work . Where is my mistake?

Answer 1

My program should log "Tick! \n" every 0.5 second.
No it shouldn't (at least not according to the code you posted). You need a run loop. Timers only fire as events on run loops. So, in your main, you need to set one up and run it.

Answer 2

Not only do you need an event loop, but you've created a timer, and you haven't scheduled it in said run loop. Instead of:
[NSTimer timerWithTimeInterval:0.5f
target:self
selector:#selector(tick:)
userInfo:nil
repeats:YES];
do this:
[NSTimer scheduledTimerWithTimeInterval:0.5f
target:self
selector:#selector(tick:)
userInfo:nil
repeats:YES];
I set your code up in the context of a Cocoa application (because it comes with a run loop), executing the TimerTest allocation in the applicationDidFinishLaunching of the delegate, and your code otherwise works.
A couple of other things: The method whose selector is passed to scheduledTimerWithTimerInterval:... should be of the form
- (void)timerMethod:(NSTimer *)aTimer
and when you're done with your timer, just invalidate it:
[timer invalidate];
though you have to keep a reference to the timer to do this, which it appears you hadn't.