Question

I have the following c# class

public class smallclass 
{
    public Vector3 var1 = new Vector3(1,2,3);
    public string var2 = "defaultval";

    public smallclass() 
    {
      var1 = new Vector3(11,22,33);
      var2 = "constructor";
    }
}

And I have another c# class

public class bigclass  
{
    public smallclass[] smallclasses;
}

Then somewhere else in my program, I increment smallclasses size with

smallclasses = new smallclass[3];

but I realize that the three elements are null…
is this correct behavior?

Allow me to clarify that I need that, whenever I resize the smallclasses array, its elements get automatically ‘constructed’… I just don’t know if such a thing can be done.

Differently than what I’d have expected, setting default values has no effect. Immediately after I resize the smallclasses array, the elements are null…

Any advice appreciated.

Thanks.

Answer 1

smallclasses = new smallclass[3]; is not resizing the array. It is creating a new array.

Your array declaration (public smallclass[] smallclasses;) creates a field in the class bigclass whose initial value is null. The statement smallclasses = new smallclass[3]; creates a new array object and assigns a reference to that object to the field smallclasses.

Whenever you create a new array of a reference type (i.e., a class), all elements of the array are null. This is expected behavior. See section 1.8 of the C# specification, which says in part: “The new operator automatically initializes the elements of an array to their default value, which, for example, is zero for all numeric types and null for all reference types.”