Question

I’m learning Objective-C and now I’m stuck with categories. Here is the code

#import <Foundation/Foundation.h>


    @interface NSMutableArray (NSMutableArrayCategory)

    -(NSMutableArray *)removeLastObject;

    @end

    #import "NSMutableArrayCategory.h"


    @implementation NSMutableArray (NSMutableArrayCategory)

    -(NSMutableArray *)removeLastObject
    {
       return [self removeObjectAtIndex:[self count] - 1];
    }
    @end

The problem is that I get

Returning void from a function with incompatible result type 'NSMutableArray' *

What is wrong here ?

Answer 1

You probably want to declare removeLastObject as returning void, not NSMutableArray.

@interface NSMutableArray (NSMutableArrayCategory)

- (void)removeLastObject;

@end

Then the implementation will look like this:

- (void)removeLastObject
{
   [self removeObjectAtIndex:[self count] - 1];
}

This matches the other mutation methods on NSMutableArray.