Question

I am creating a very simple calculator. To save the first user inputed float, i save it as a string in the addition action as to save it when they click on the addition button. Then later I call upon it again to add it to the second user inputed float. However when i call upon it again it gives the error: Use of undefined identifier num1. The same thing happens with the operation integer. Here is the relevant code:

- (IBAction)addition {

    NSString *number1 = total.text;
      float  num1 = [number1 floatValue];
    int operation = 1;
    total.text = @"";

}

- (IBAction)equal {

    NSString *number2 = total.text;
    float num2 = [number2 floatValue];

    if (operation == 1) {
        int num3 = num1 + num2;


    NSString *znumber1 = [NSString stringWithFormat:@"%f", num1];
}

Answer 1

You need to declare num1 as an “instance variable” so it’s accessible by both functions (usually declared within your @interface block).

The way you’re declaring it only allows for the code within that function’s scope to access it.

I would reccomend reading up on variable scope before continuing.