打字稿静态循环锁

Question

此代码是对status（OrderStatus.keys）字符串进行比较的一种简单尝试。状态更新只能向前移动。因此，如果等待批准在批准之后到来，则可以拒绝。
构造函数由于对象创建的锁定而引发错误。
如何解决？

export class OrderStatus{

    private static keys = ['draft', 'waiting-approval', 'approved', ..];
    private static keyMaps = {};

    static DRAFT  = new OrderStatus(OrderStatus.keys[0], 1); // execution starts here
    static WAITINGAPPROVAL = new OrderStatus(OrderStatus.keys[1], 2);
    static APPROVED = new OrderStatus(OrderStatus.keys[2], 3);

    private constructor(private _key: string, private _index: number) {
        this.initialize(); // error on run
    }

    private initialize(){
        OrderStatus.keyMaps[OrderStatus.keys[0]] = OrderStatus.DRAFT; // draft object not yet ready because of above static block
        OrderStatus.keyMaps[OrderStatus.keys[1]] = OrderStatus.WAITINGAPPROVAL;
        OrderStatus.keyMaps[OrderStatus.keys[2]] = OrderStatus.APPROVED;
    }

    static resolve(key : string) : OrderStatus {
        return OrderStatus.keyMaps[key];
    }

    get index() {
        return this._index;
    }

    toString() {
        return this._key;
    }

    compare(value1: OrderStatus){
        return value1.index < this.index ? -1 : (value1.index > this.index ? 1 : 0);
    }