IOS set same but different objects to one memory address - iphone

Question

#interface ClassWithTimer : NSObject {
}
-(void) startTimer;
-(void) stopTimer;
#end
#implementation ClassWithTimer
NSTimer *up;
-(void) startTimer{
up = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(doSomething) userInfo:nil repeats:YES];
-(void) stopTimer{
[up invalidate];
}
- (void) doSomething{}
#end
then i do
- (IBAction)startTimers:(id)sender {
timer1 = [[ClassWithTimer alloc] initWithName:#"time1"];
timer2 = [[ClassWithTimer alloc] initWithName:#"time2"];
[timer1 startTimer];
[timer2 startTimer];
[timer1 stopTimer];
[timer2 stopTimer];
}
When i stop the timers i see that timer1 the same for timer2 and the invalidate method throw exception in [timer2 stopTimer] because this object invalidated at this moment.
I know that this is iOS policy but i can't find documentation for this.

Answer 1

Move
NSTimer *up;
into your .h file inside the interface block.

Answer 2

NSTimer needs to be an iVar, you are just declaring freely in the class allowing the two classes to share the same timer. Also you need to release the previous timer then retain the new one in startTimer.
#interface ClassWithTimer : NSObject {
NSTimer *up; //Declare iVar(instance variables) here
}
-(void) startTimer;
-(void) stopTimer;
#end
#implementation ClassWithTimer
-(void) startTimer{
[up invalidate];
[up release];
up = [[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(doSomething) userInfo:nil repeats:YES] retain];
-(void) stopTimer{
[up invalidate]; //Do these same this line
[up release]; //and this line in your dealloc
up = nil;
}
- (void) doSomething{}
#end