Question

I’m relatively new to Objective-C so this might be really simple to do: I have a text box in my application that displays an ammo count, so each time the user taps a fire button the number in the text box will go down by one (12 > 11 > 10, etc) to 0. I have tried using for and if statements, but they are not working (I may have used incorrect syntax). This is what I’m using right now, but obviously I need the

- (IBAction)fire {

    [ammoField setText:@"11"];

}

- (IBAction)reload {

    [ammoField setText: @"12"];

}

Answer 1

The simplest way would be to convert the text to a number, decrement that and the reset the text, i.e. replace the code in the fire method with:

NSInteger ammoCount = [ammoField.text integerValue];
ammoCount--;
ammoField.text = [NSString stringWithFormat:@"%d", ammoCount];

But don’t do this, it will make baby Steve Jobs cry.

A better way would be to add a new variable to the class of type UIInteger that tracks the the number of bullets, i.e.:

// in interface
NSInteger _ammoCount;

...

// in implementation

- (IBAction)fire {
    _ammoCount--;
    if (_ammoCount <= 0) {
        _ammoCount = 0;
        fireButton.enabled = NO;
    }
    [ammoField setText: [NSString stringWithFormat:@"%d", _ammoCount]];
}

- (IBAction)reload {
    _ammoCount = 12;
    [ammoField setText: [NSString stringWithFormat:@"%d", _ammoCount]];
    fireButton.enabled = YES;
}

Oh, and don’t forget to call reload at some point early on to ensure _ammoCount and ammoField get initialised.