Question

伪代码

doStuff() {
  // A is an asynchronous call
  A
  .then(result_a => { // process result_a })
  .then(result_b => { // process result_b })
  .then(() => { // side_effects})
}

如何返回result_b？

背景

我正在使用TypeORM将订单和订单行保存到sqlite数据库中，用于angular + electron桌面应用程序。我认为这不是特定于Angular的。除了以非常线性的方式链接它们之外，我对使用then不太熟悉。

问题陈述

如何返回then链中间的purchase_order？我正在寻找这个或purchase_order.id。

简化版本：

addOrder(header: PurchaseOrder, lines: PurchaseOrderLine[]) {
  const new_order = new PurchaseOrder();

  this.databaseService.connection
    .then(conn => conn.manager.save(new_order))
    .then(purchase_order => {
      let new_lines = lines.map(line => {
        const new_order_line = new PurchaseOrderLine();
        this.databaseService
          .connection
          .then(conn => conn.manager.save(new_order_line));
      })
    })
    .then(() => this.reflectChanges());
}

完整版：

addOrder(header: PurchaseOrder, lines: PurchaseOrderLine[]) {
  const new_order = new PurchaseOrder();

  // copy header details to new order
  new_order.purchase_order_date = (<any>header.purchase_order_date).format();
  new_order.total_value = header.total_value;
  if(header.delivery_required_by) {
    new_order.delivery_required_by = (<any>header.delivery_required_by).format();
  }
  new_order.notes = header.notes;
  new_order.supplier = _state.selectedSupplier;

  // use databaseService to save order and then save the order lines
  this.databaseService
    .connection
    .then(conn => conn.manager.save(new_order))
    .then(purchase_order => {
      let new_lines = lines.map(line => {
        const new_order_line = new PurchaseOrderLine();

        new_order_line.quantity = line.quantity
        new_order_line.code = line.code
        new_order_line.file_no = line.file_no
        new_order_line.description = line.description
        new_order_line.unit = line.unit
        new_order_line.rate = line.rate
        new_order_line.total = line.total
        new_order_line.note = line.note
        new_order_line.purchase_order = purchase_order

        this.databaseService
          .connection
          .then(conn => conn.manager.save(new_order_line));
      })
    })
    .then(() => this.reflectChanges());
}

如何在Angular的“ then”链中返回？

0 个答案: