Question

I’m fairly new to coding with Objective-C/Xcode, so I’m just trying my luck with the easy stuff, making sure I get it before moving on to something harder.

What I am trying at the moment is to make a calculator. I’ve done one of those simple ones where there are two text boxes and an equals button, so I’m trying a number pad calculator now.

What I’m stuck on is how to ADD a number to a label (NEXT TO ALL THE OTHER NUMBERS, NOT ADDED) when the corresponding button is pressed. I can manage to add one number, but not both.

At the moment, I am only experienced with vb.net, so I’m used to

label.text = label.text & 1

I’m not sure how to do this is in Xcode.

Any help, code hints, links (or code chunks :P) would be appreciated.

Answer 1

Don’t add the number to the label. Instead, have another variable which is your running total which is a number and then update the label with the text version of the number. A good habit to get into is separating your presentation (view) from your data (model). In this trivial example, create a variable to hold your data and make the UI reflect that. Don’t use the label as your model.

As a simple code example, let’s say I had an increment button and I wanted it to increment the value of the label. The action for the button is the IBAction increment function.

Header:

@interface CrapletViewController : UIViewController
{
    NSInteger _total;
}

@property (nonatomic, retain) IBOutlet UIButton *myButton;
@property (nonatomic, retain) IBOutlet UILabel *label;

- (IBAction)increment:(id)sender;

Implemenation:

- (IBAction)increment:(id)sender
{
    _total++;
    NSLog(@"total");
    [label setText:[NSString stringWithFormat:@"total: %d", _total]];
}