node.js - 如何避免多个 Mongoose 操作的嵌套承诺？

Question

很抱歉，我知道已经有一些帖子处理 NodeJS 中的嵌套承诺问题，但我仍然无法理解这一点。
我正在使用 Express 和 Mongoose，我想找到一个对象 ID，然后保存一个对象，然后更新另一个对象，但我不明白我应该如何做得比这更好，因为这些是依赖的承诺：

        // Get Client object ID from email
        Client.findOne({ email: req.body.clientEmail })
          .exec()
          .then((client) => {
            // Then add Client ID to program and save
            const program = new Program(req.body);
            program.Client = client._id;
            program.save()
              // Finally add the program to the existing coach user
              .then((program) => {
                Coach.updateOne({ _id: req.session.userId }, { $push: { programs: program._id } },
                  function (err, coachUpdated) {
                    if (err) return handleError(err);
                    console.log(coachUpdated);
                  })
              })
              .then(() => { res.send('New program added!'); });
          })

提前致谢

标签： node.jsexpressmongoosepromisenested

Answer 1

简单，使用async/await我会做类似的事情

const client = await Client.findOne({ email: req.body.clientEmail })
          .exec();
const program = new Program(req.body);
program.Client = client._id;
const {_id} = await program.save();
//If this is not a promise. you can still use `promisify` from `utils` standard node.js lib to make it a promise
// and then call it with await. :) 
Coach.updateOne({ _id: req.session.userId }, { $push: { programs: _id } },
    function (err, coachUpdated) {
      if (err) return handleError(err);
      console.log(coachUpdated);
})
//You can choose to place it inside the callback above.
res.send('New program added!');

注意：外包装函数应以asynclike为前缀async function (req, res) {...