Simple compile error in class constructor

Question

I have a very simple class that wont compile because of a default parameter in the constructor. The language is C# and the class will be used in a Unity3d game. So this compile error is occurring in Unity's "IDE"

Compile Error:

Assets/Utilities/GenericClasses.cs(30,94): error CS1736: The expression being assigned to optional parameter `nName' must be a constant or default value

public class Element {
    public static readonly string NULL_NAME = "___NULL_NAME___";
    public enum elementType {E_ELEMENT, E_MODEL, E_VIEW, E_SUPER, E_ARC};
    private string name;
    private elementType type;

    // line 30 is below
    public Element(elementType nType=elementType.E_ELEMENT, string nName=NULL_NAME) {
        type = nType;
        name = nName;
    }
}

What am I doing wrong?

Darin Dimitrov · Accepted Answer · 2012-06-11 06:05:10Z

1

You should use a constant value instead of a static readonly:

public const string NULL_NAME = "___NULL_NAME___";

The reason why your code doesn't compile is because you attempted to assign a non constant default value to the nName parameter in the constructor which is not supported.

answered Jun 11, 2012 at 6:05

Darin Dimitrov

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Comments

Emond · Accepted Answer · 2012-06-11 06:07:19Z

1

NULL_NAME is not a constant, it is readonly.

A readonly variable can be initialized in the constructor so it is not known at compile time which is required for a default value for an optional parameter because the compiler will substitute the value where it is omitted in a call.

answered Jun 11, 2012 at 6:07

Emond

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Comments

k0stya · Accepted Answer · 2012-06-11 06:05:31Z

0

Try this one

public const string NULL_NAME = "___NULL_NAME___";

answered Jun 11, 2012 at 6:05

k0stya

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