Getter that returns a copy of an object

[Chuck]

Stupid question, and maybe I'm just not thinking this through properly, but on page 168-169, there is mention of writing a getter that returns a copy of an object so that you don't inadvertently modify instance variables of the source object reference. How can this be accomplished?

Is this how?

Code: (Objective-C)

-(XYPoint *) origin
{
  return (XYPoint *) origin;
}

[skochan]

Code: (Objective-C)

-(XYPoint *) origin
{
     XYPoint *copiedPoint = [[XYPoint alloc] init];

     copiedPoint.x = origin.x;
     copiedPoint.y = origin.y;

     return copiedPoint;
}

[lessisv]

Would it be the same if we wrote this??  :

Code: (Objective-C)

-(XYPoint *) origin  
{  
     XYPoint *copiedPoint = [[XYPoint alloc] init];  
  
     copiedPoint = origin;  
  
     return copiedPoint;  
} 

[happyzhb]

Nope, the point here is to init a new XYPoint instance, use the setter method to give the same x and y as the origin, then return the new instance.

If you point your new instance to the original origin object, you didn't do copy, you are returning the same source object reference, the 05 line of your code does not create a "copy", it simply make the copiedPoint instance you just init point to the very same object or "origin".

Hope that is clear.