Method 'while' touching screen - ios

Question

I'm making a game using Xcode for iOS. This is a segment of code I have that makes the sprite jump up when the screen is tapped:
//tap/touch to jump (& play sound)
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *) event{
[self playSound];
jumpUp = 16;
}
How can I implement it so that the sprite just keeps going up whist you are touching the screen instead of just a single tap?
//Pseudo code:
while touchingScreen {
jumpUp +=1;
}

Answer 1

You need to start some kind of loop in touchesBegan that runs while the touch is lasting. Then in touchesEnded (and cancelled!) make that loop stop. You can use a repeating NSTimer or something like the following. You may need to do some adjustments to make it smooth enough for a game.
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
[super touchesBegan:touches withEvent:event];
// touching is a BOOL that keeps track of the touch event
// YES means that a touch is happening at the moment
touching = YES;
dispatch_async(dispatch_get_main_queue(), ^{
[self performSelector:#selector(up) withObject:nil afterDelay:.0];
});
}
- (void)up {
// move your sprite further up
NSLog(#"up");
if (touching) {
// if the user is still touching repeat moving the sprite up
[self performSelector:#selector(up) withObject:nil afterDelay:0.1];
}
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
[super touchesEnded:touches withEvent:event];
// The finger was lifted, stop the up movement
touching = NO;
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
[super touchesCancelled:touches withEvent:event];
touching = NO;
}