Question

I am creating a calculator app and the calculator screen is a UILabel. I am having trouble with a delete key. Here is my Code:

.h

IBOutlet UILabel *display;

.m

- (IBAction)Del 
{
    [display.text substringToIndex:display.text.length -1];
}

it has no errors and runs in the simulator perfectly but does not actually work. Can anyone help.

Answer 1

You are ignoring the return value of the substringToIndex: method and you do not update the label’s text.

You want something like this:

- (IBAction)Del {
    NSString *oldText = display.text;
    if (oldText.length > 0) {
        NSString *newText = [oldText substringToIndex:oldText - 1];
        display.text = newText;
    }
}

This also guards against trying to delete from an empty label.