How can I instantiate immutable mutually recursive objects?

Question

I have an immutable recursive type:

public sealed class Foo
{
    private readonly object something;
    private readonly Foo other; // might be null

    pu         


        

Answer 1

Below is an example of a class Foo with write-once immutability rather than popsicle immunity. A bit ugly, but pretty simple. This is a proof-of-concept; you will need to tweak this to fit your needs.

public sealed class Foo
{
    private readonly string something;
    private readonly Foo other; // might be null

    public Foo(string s)
    {
        something = s;
        other = null;
    }

    public Foo(string s, Foo a)
    {
        something = s;
        other = a;
    }
    public Foo(string s, string s2)
    {
        something = s;
        other = new Foo(s2, this);
    }
}

Usage:

static void Main(string[] args)
{
    Foo xy = new Foo("a", "b");
    //Foo other = xy.GetOther(); //Some mechanism you use to get the 2nd object
}

Consider making the constructors private and creating a factory to produce Foo pairs, as this is rather ugly as written and forces you to provide public access to other.