如何依次调用一个异步函数？

Question

这是我所拥有的：

  ngOnInit() {
    this._addServ.getDefaultAddress().subscribe((res)=>{
      if(res.status){
        //I need these next two functions to finish their async API requests 
        //before selectNormalDelivery is called
        this.selectShippingAddress();
        this.selectBillingAddress();
        this.selectNormalDelivery();
      }
    })
  }

我需要selectShippingAddress和selectBillingAddress完成他们的通话，然后才能调用selectNormalDelivery。我该怎么做？我不想将它们转换为Promise，因为它们在其他时间被称为无需链接。这涉及到.then吗？

这是这些功能的代码：

  selectShippingAddress(){
    this.addressService.setShippingAddresses(this.cartService.shippingAddress.address_id).subscribe((res) => {
      console.log('Set shipping address!')
      console.log(res);
    }, err => {
      console.log('Failed to set shipping address')
      console.log(err);
    })
  }

  selectBillingAddress(){
    this.addressService.setPaymentAddresses(this.cartService.billingAddress.address_id).subscribe((res) => {
      console.log('Set billing address!')
      console.log(res);
    }, err => {
      console.log('Failed to set billing address')
      console.log(err);
    })
  }

如果尝试使用.then，则会收到错误Property 'then' does not exist on type 'void'.，这很有意义，因为我没有尝试返回任何东西，我只需要他们为API来完成调用。

建议？

Answer 1

ngOnInit() {
    this._addServ.getDefaultAddress().subscribe((res)=>{
        if(res.status){
            Promise.all(this.selectShippingAddress(),this.selectBillingAddress()).then((results /* array of results */) => {
                this.selectNormalDelivery();
            }).catch(() => {
                 //one of the promises rejected
            })
        }
    })
}

和

selectShippingAddress(){
    return new Promise((resolve, reject) => {
        this.addressService.setShippingAddresses(this.cartService.shippingAddress.address_id).subscribe((res) => {
            resolve(res);
        }, err => {
            reject(err);
        });
    })
}

selectBillingAddress与setShippingAddresses类似