Obj-C function declaration in header

Question

I am trying to put a C-style function in the header of an Objective-C class. (My terminology might be wrong here -- I'm just used to writing Objective-C class methods rather than functions). It looks as follows:

// Sort function
NSInteger sort(NSString *aString, NSString *bString, void *context);

NSInteger sort(NSString *aString, NSString *bString, void *context) {
    return [aString compare:bString options:NSNumericSearch];
}

Unforuntately this results in:

Expected '=', ',', ';', 'asm' or 'attribute' before '{' token

Any ideas as to what I'm missing? Thank you.

Answer 1

My guess is that you put the function definition within the @interface of your class. Instead, make sure C style function declarations are outside of Objective-C @interface declarations:

// declare C functions here
NSInteger sort(NSString *aString, NSString *bString, void *context);

@interface MyClass : NSObject
{
  // class instance vars
}

// class properties & instance methods
@end

Answer 2

The body of your function needs to be in the .m file instead of in the header.

As long as the declaration of your function (NSInteger sort(NSString *aString, NSString *bString, void *context);) remains in the header you'll still be able to access the sort function from anywhere you import the header.