iOS 5 Programming Cookbook

1.14. Defining Two or More Methods with the Same Name

Problem

You would like to implement two or more methods with the same name in one object. In object-oriented programming, this is called method overloading. However, in Objective-C, method overloading does not exist in the same way as it does in other programming languages such as C++.

Solution

Use the same name for your method, but keep the number and/or the names of your parameters different in every method:

- (void) drawRectangle{

  [self drawRectangleInRect:CGRectMake(0.0f, 0.0f, 4.0f, 4.0f)];

}

- (void) drawRectangleInRect:(CGRect)paramInRect{

  [self drawRectangleInRect:paramInRect
                  withColor:[UIColor blueColor]];

}

- (void) drawRectangleInRect:(CGRect)paramInRect
             withColor:(UIColor*)paramColor{

  [self drawRectangleInRect:paramInRect
                  withColor:paramColor
                  andFilled:YES];

}

- (void) drawRectangleInRect:(CGRect)paramInRect
                   withColor:(UIColor*)paramColor
                   andFilled:(BOOL)paramFilled{

  /* Draw the rectangle here */

}

This example shows a typical pattern in overloading. Each rectangle can be drawn either filled (solid color) or empty (showing just its boundaries). The first procedure is a “convenience procedure” that allows the caller to avoid specifying how to fill the rectangle. In our implementation of the first procedure, we merely call the second procedure, making the choice for the caller (andFilled:YES) The second procedure gives the caller control over filling.

Discussion

You can define two methods with the same name so long as they ...