Question

I’m currently learning myself objective-c and iOS programming and found myself stuck with non-working code due to this subtle error for an hour.
Consider the following code:

@property (strong, nonatomic) NSString *name;
- (NSString *):name { return @"Some name"; }

At first glance (and for anyone new) this looks like an overridden getter for the name property. But theres a very subtle : that shouldn’t be there. You get no warning/error from the compiler/parser/runtime here, so my question is what does this actually end up as?

I tried to figure a way of calling this method once I saw the error, but didn’t succeed in my few attempts.

Answer 1

The method signature - (NSString *):name breaks down to the following:

• - It is an instance method (versus a class method with a +).
• (NSString *) It returns a string.
• : If you were to speak the name of this method, it would simply be called “colon”. : tells the compiler that your method accepts one parameter as well.
• name There is a parameter called name.

When you don’t specify a type, the compiler assumes you meant id, so this method actually fleshes out to be - (NSString *):(id)hello

A valid call to this method would be: [self :@"hello"].

You can do really weird things because : is a valid name for a method, and the compiler assumes id. You could, if you really wanted to, have a method called - :::. The compiler would assume you meant - (id):(id):(id):(id), a method that returns an object of type id and takes three parameters of type id. You’d call it like so: [self :@"hello" :anObject :myObject];