Advice on struct fields in classes

[Marcus Andr?n]

Recently I was trying to figure out why a small program I had written
didn't work. It was a simple problem really, normalizing the length of
a couple of coordinates in a vector system and I just couldn't figure
out why the coordinates refused to be changed. Suddenly it hit me what
an idiot I had been as I noticed that the Coordinate structure that I
was trying to change was declared as a property. I was basically
calling the Normalize method on a copy of the class field instead of
on the field itself.

public struct Coordinate{
public void Normalize();
}

public class MyObject
{
private Coordinate coord;
public Coordinate Coord{
get;set;
}
}

MyObject obj = new MyObject()
obj.Coord.Normalize() <--------- Incorrect


After having looked at the different kinds of solutions I decided to
ask this group for opinions on the best way to solve this problem.
First though, I will present what I did come up with during my
brainstorming.

The simplest fix is probably to just expose the Coordinate field
directly and not use property at all. This is however a breach of OO
and could cause problems, for example if I wanted to expose a
Coordinate field in an interface.

A second alternative is to convert it from a struct to a class. This
would of course introduce problems when passing coordinates as
parameters in functions and that makes me vary of this approach.

The last alternative I could think of is to return a new struct value
from the Normalize function that the Property can be set to.

public Coordinate Normalize();
or
public static Coordinate Normalize(Coordinate coord);

The main disadvantage with this alternative is that it is quite a lot
slower than the above versions which could cause a problem if
Normalizing lots of values.

So far I am leaning towards using the static version unless I finds
out that it is a performance bottleneck but I would very much like to
hear other opinions or suggestions.

 

[Dennis Myrén]

You could provide the methods of the struct directly in class MyObject
and totally hide the instance of the structure, eg:
MyObject myInstance = new MyObject();
myInstance.NormalizeCoords();

function MyObject.NormalizeCoords:
public void NormalizeCoords ( )
{
_coords.Normalize();
}

 

[codymanix]

You can either make Coord a class or do the following:

MyObject obj = new MyObject()
Coord c = obj.Coord;
c.Normalize();
obj.Coord = c;