iOS Really weird error

[xcodeNewbie]

I've been having trouble getting the following bit of code to work right:

for (Planet *aPlanet in planetArray) {
        [aPlanet.makeShipTimer invalidate];
}

It always crashes when it runs this part. So I tried it like this:

for (Planet *aPlanet in planetArray) {
        if ([aPlanet.makeShipTimer isValid]) [aPlanet.makeShipTimer invalidate];
}

And it still crashes. So I added an NSLog:

for (Planet *aPlanet in planetArray) {
        if ([aPlanet.makeShipTimer isValid]) NSLog(@"Valid!");
}

And the NSLog shows up, which means that the timer is valid. Any idea what's going on?

 

[jiminaus]

My first thought is that the Planet objects have been deallocated. Run your program under Instruments using the zombies template.

isValid returning true doesn't contradict my theory. The behaviour of sending a message to a deallocated object is undefined.

isValid doesn't check if the timer is still allocated, it only checks if the timer is still capable of firing. This could be simply returning a BOOL ivar. That could be why your program doesn't crash at this point.

 

[xcodeNewbie]

Dealloced Planets

Thanks for your reply, but I already ran an NSLog test that confirmed the planets still exist.

 

[jiminaus]

but I already ran an NSLog test that confirmed the planets still exist.

How did you do that? That NSLog code you posted above does not check whether the object exists.

 

[RonC]

I've been having trouble getting the following bit of code to work right:

for (Planet *aPlanet in planetArray) {
        [aPlanet.makeShipTimer invalidate];
}

It always crashes when it runs this part. So I tried it like this:

A couple of thoughts:
When you say it crashes, what do you mean? Do you get a stack backtrace in the console output? Care to share?

Have you run it under the debugger, with a breakpoint on both the line within the for loop? You can re-write that code slightly to make debugging a little easier, something like:

for (Planet *aPlanet in planetArray) {
        NSTimer *makeShipTimer = [aPlanet.makeShipTimer]; // guessing on type
        [makeShipTimer invalidate];
}

You can set the breakpoint on the invalidate statement and see the result of the makeShipTimer call.

 

[KoolStar]

It also depends on what properties that the op declared in the header for the nstimer as well as if he is setting to nil anywhere after he invalidates the timer.