Question

I am writing an iOS app for the iPhone in Xcode and I have created some classes as well as their methods inside their respective .h and .m files (that’s two classes so basically I have two pairs of .h & .m files)

I now I want to start writing my main loop that will be executed whenever the user hits on the play button, but where exactly do I do that ?

Do I do that in ViewController.m ? e.g. inside this method :

- (IBAction)playPressed:(UIButton *)sender 
{
    // main loop executed in here ?
    // or simply message to the main loop to start executing is *sent* from here ?
}

I read about a similar question in here and someone was suggesting AppDelegate. Now would that be AppDelegate.m or AppDelegate.h ? And if that’s the case do I just start writing code or do I include everything inside something like :

int main(int argc, char **argv)
{
   ....
}

in the Appdelegate file?

I tried to simply start instantiating classes and declaring generic methods (not belonging to any particular class that is..) in a game.m file I created and I get a initializer element is not a compile-time constant warning as soon as I try instantiating anything

Any help? Coming from c++ it would really help me to clarify once and for all in which file exactly to write my main loop and whether I should wrap it in some kind of an int main() function..

thanks!

PS :

Just in case it makes any difference, my ViewController will only consist of a play button that would start the execution of my main loop whenever its pressed, and a stop button that would terminate the execution of the main loop

I have created their respective methods in ViewController.m :

- (IBAction)playPressed:(UIButton *)sender 
{
    // 
}

- (IBAction)stopPressed:(UIButton *)sender 
{
    //  ??
}

which are for the time being empty 🙂

Answer 1

The programming methodoly on iOS is different from the C++ methodoly.
In C++ , indeed , you would have to make an infinite loop and get the touches , draw everything , etc at each frame.
Until the player presses “exit” and you break the loop.
On iOS , things are done differently:
You already have a main.m file in which you have a main function.
That starts up the app delegate. That app delegate tells you when the app finished launching , goes to background , comes in foreground , etc.
When the app finished launching , you go to your first actual screen.
There , you ADD subviews. You don’t draw them at each frame. That is done automatically for you once you have added the view to a parent view.
The programming on iOS is based on events. You don’t have to check for touches and see if the
touch location is on a button and then call the method of that button.
Instead , you set a callback method for the button and it’s called automatically for you once the button is pressed.
Of course , you first need to alloc the button and add it to a parent view.

Once you get used to this event based programming model , you will for sure like it.
At the start it may seam very different and maybe it doesn’t make sense to you , but don’t worry.
Comming from a C++ background is surely a good start.

Cheers,

George

EDIT: In that case , I can give more specific info:
So , you go from the AppDelegate in your first screen. Let’s call it MainAppScreen.
Now , you need to add those 2 buttons and set selectors ( callback methods ) for them. I can see you already did that.

Now :

- (IBAction)playPressed:(UIButton *)sender
{
    running = TRUE;
    [self performSelectorInBackground:@selector(myLoop) withObject:nil];
}
- (IBAction)stopPressed:(UIButton *)sender 
{
    running = FALSE;
}
- (void) myLoop
{
    while(running)
    {
       //this is your loop. You can code in here.
    }
}

Where running is an instance variable in the MainAppScreen class.

Hope this helps.

Cheers!