Question

I’m starting to develop for the iPhone. I have a beginner-type question, I’m sure:

I have this, which works:

testLabel.text = [NSString stringWithFormat:@"%@ to %@", testLabel.text, newLabelText];

I wish I could use the “+=” operator, but I get a compile error (Invalid operands to binary +, have ‘struct NSString *’ and ‘struct NSString *’):

testLabel.text += [NSString stringWithFormat:@"to %@", newLabelText];

Why can’t I do this?

Also, how can I shorten my first snippet of code?

Answer 1

You can’t use the += operator because C and Objective-C do not allow operator overloading. You’re trying to use += with two pointer types, which is not allowed — if the left-hand side of a += expression has a pointer type, then the right-hand side must be of an integral type, and the result is pointer arithmetic, which is not what you want in this case.