So, I'm fairly certain that if I plan on manipulating strings often, such as with stringByAppendingString, I should be using variables of type NSMutableString.
But what if I'm doing something like this?
UILabel *someLabel = [[UILabel alloc] init];
[someLabel setText: [[someDictionary objectForKey:@"some_key"] stringByAppendingString:@"some other string"];
I read that if you use stringByAppendingString on an NSString, you end up with leaks because the pointer associated with the initial NSString moves around, pointing to the new string created by the append, whereas with NSMutableString, your pointer always points to that mutable string.
So my question is, what is implicitly happening when I call stringByAppendingString on something that is a string, but not explicitly an NSString or an NSMutableString? Such as, in my above case, the value of some key in a dictionary. Is doing this wrong, and should I be doing something like below?
[[[NSMutableString stringWithString:[someDictionary objectForKey:@"some_key"]] stringByAppendingString:@"some other string"]]
I've always been a fan of [NSString stringWithFormat@"%@%@", a, b]; because then you clearly get a new autoreleased string and can dispose of "a" and "b" correctly.
With [someDictionary objectForKey:@"some_key"], you will be getting the type of object that was put into that dictionary originally. So blindly calling stringByAppendingString without knowledge of what's in that dictionary seems like a bad idea.