Bluebird：在一个循环中链接 .then 处理程序

Question

问题：如何将getNextPaymentPayload/makePayment/confirmPayment链接成一个循环？您始终可以使用 hasAnyPayments 方法检查是否还有任何付款。

问题： 您不能并行付款。要进行付款，您需要等待前一个付款完成。

示例：

SomeService
    //first payment
    .getNextPaymentPayload()
    .then(paymentPayload => this.makePayment(paymentPayload))
    .then(paymentResponse => this.confirmPayment)
    //second payment        
    .then(SomeService.getNextPaymentPayload())
    .then(paymentPayload => this.makePayment(paymentPayload))
    .then(paymentResponse => this.confirmPayment)
    //so on...

---

Answer 1

假设 hasAnyPayments 将 return 一个最终解析为布尔值的 Promise：

let doPayments = () => {
    return hasAnyPayments().then((hasAny) => {
        if (!hasAny) {   
            return Promise.resolve();        // all done
        } else {
            return SomeService.getNextPaymentPayload()
                      .then(paymentPayLoad => this.makePayment(paymentPayLoad))
                      .then(paymentResponse => this.confirmPayment(paymentResponse))
                      .then(doPayments);     // "recurse"
        }
    }
}