Question

So I got into a friendly argument with a co-worker over a piece of code:

public sealed class NewObject
{
    private string _stuff = string.Empty;

    public string Stuff
    {
        get { return GetAllStuff(); }
    }

    private string GetAllStuff()
    {
        //Heavy string manipulation of _stuff
    }

    public NewObject(string stuffToStartWith)
    {
        _stuff = stuffToStartWith;
    }

    public static NewObject operator +(NewObject obj1, NewObject obj2)
    {
        if (obj1 == null)
            throw new ArgumentNullException();

        if (obj2 == null)
            throw new ArgumentNullException();

        NewObject result = new NewObject(string.Empty);
        result._stuff = String.Concat(obj1._stuff, obj2._stuff);

        return result;
    }
}

The argument was over the operator override. My co-worker feels that it’s not best programming practice to set values of private fields anywhere but the constructor. The solution proposed by my co-worker was to refactor the name of the Stuff property to AllStuff and add a property, Stuff, that has a get AND set accessor and use the new Stuff property in the operator override. Making it look like this:

    public static NewObject operator +(NewObject obj1, NewObject obj2)
    {
        if (obj1 == null)
            throw new ArgumentNullException();

        if (obj2 == null)
            throw new ArgumentNullException();

        NewObject result = new NewObject(string.Empty);
        result.Stuff = String.Concat(obj1.Stuff, obj2.Stuff);

        return result;
    }

I disagree. I feel the first way is better since it keeps the property read-only outside the class. My question is, which way is the best practice for object-oriented design?

Answer 1

You could give yourself a private set on the property (which would retain visibility or lack thereof while allowing you to use property syntax), but that doesn’t really address the point.

Within the class, I say that variables are fair game. Anywhere outside, including inherited classes, should get and set the property, but within the declaring class I say it’s OK to assign the private member.