node.js - Nodejs promise 类型错误 : Cannot read property 'then' of undefined

Question

当我尝试在我的route 中访问controller 的功能时出现错误。我用 Mongoose ， express 。

错误:

TypeError: Cannot read property 'then' of undefined at /private/var/www/html/sms/server/routes/user.routes.js:70:9 at Layer.handle [as handle_request] (/private/var/www/html/sms/node_modules/express/lib/router/layer.js:95:5) at next (/private/var/www/html/sms/node_modules/express/lib/router/route.js:137:13) at Route.dispatch (/private/var/www/html/sms/node_modules/express/lib/router/route.js:112:3) at Layer.handle [as handle_request] (/private/var/www/html/sms/node_modules/express/lib/router/layer.js:95:5) at /private/var/www/html/sms/node_modules/express/lib/router/index.js:281:22 at Function.process_params (/private/var/www/html/sms/node_modules/express/lib/router/index.js:335:12) at next (/private/var/www/html/sms/node_modules/express/lib/router/index.js:275:10) at Function.handle (/private/var/www/html/sms/node_modules/express/lib/router/index.js:174:3) at router (/private/var/www/html/sms/node_modules/express/lib/router/index.js:47:12) at Layer.handle [as handle_request] (/private/var/www/html/sms/node_modules/express/lib/router/layer.js:95:5) at trim_prefix (/private/var/www/html/sms/node_modules/express/lib/router/index.js:317:13) at /private/var/www/html/sms/node_modules/express/lib/router/index.js:284:7 at Function.process_params (/private/var/www/html/sms/node_modules/express/lib/router/index.js:335:12) at next (/private/var/www/html/sms/node_modules/express/lib/router/index.js:275:10) at /private/var/www/html/sms/server.js:65:3 POST /api/user/create 500 27.274 ms - 16 (node:11300) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: This email is already exists. Please enter another email. (node:11300) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

这是我的代码:-

user.cont.js

function create(data) {
  User.findOne({ email: data.email })
    .exec((err, doc) => {
      if (err) {
        return new Promise((resolve, reject) => {
          return reject(err);
        })
      } else {
        if (doc) {
          return new Promise((resolve, reject) => {
            return reject(new Error('This email is already exists. Please enter another email.'));
          })
        } else {
          const user = new User(data);
          return user.save()
        }
      }

    })

}


export default { getUsers, create };

user.route.js

router.post('/create', (req, res, next) => {
        UserCtrl.create(req.body)
            .then(savedUser => res.json(savedUser)) . // here error is generated
            .catch(e => next(e));
    });

Answer 1

您应该将整个 User.findOne() 调用包装在 Promise 中，如下所示:

function create(data) {
  return new Promise((resolve, reject) => {
    User.findOne({ email: data.email })
      .exec((err, doc) => {
        if (err) return reject(err)
        if (doc) return reject(new Error('This email is already exists. Please enter another email.'))
        const user = new User(data)
        user.save((err) => {
          if (err) return reject(err)
          resolve()
        })
      })
  })
}

您还需要解决 promise ，否则您的 UserCtrl.then() 调用中的回调将永远不会被调用。我还添加了错误处理，以防将新的 User 保存到数据库时出现问题。