module main

interface IGameObject {
mut:
    name     string
    parent   ?&IGameObject
    children []&IGameObject
    add_child(mut o IGameObject)
    advance()
}

@[heap]
struct GameObject implements IGameObject {
mut:
    name     string
    parent   ?&IGameObject
    children []&IGameObject
}

fn (mut gameobject GameObject) add_child(mut o IGameObject) {
    o.parent = &gameobject
    gameobject.children << o
}

fn (mut gameobject GameObject) advance() {
    if gameobject.parent != none {
        eprintln('parent:  ${gameobject.parent.name} ')
    }
    for mut child in gameobject.children {
        child.advance()
    }
}

fn test_main() {
    mut v1 := &GameObject{
        name: 'v1'
    }
    mut v2 := &GameObject{
        name: 'v2'
    }
    v1.add_child(mut v2)
    v1.advance()
    assert true
}