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

You can do it by adding a constructor overload that accepts a function, and passing the this reference to that function. Something like this:

public sealed class Foo {
    private readonly object something;
    private readonly Foo other;

    public Foo(object something, Foo other) {
        this.something = something;
        this.other = other;
    }

    public Foo(object something, Func makeOther) {
        this.something = something;
        this.other = makeOther(this);
    }

    public object Something { get { return something; } }
    public Foo Other { get { return other; } }
}

static void Main(string[] args) {
    var foo = new Foo(1, x => new Foo(2, x)); //mutually recursive objects
    Console.WriteLine(foo.Something); //1
    Console.WriteLine(foo.Other.Something); //2
    Console.WriteLine(foo.Other.Other == foo); //True
    Console.ReadLine();
}