Question

我有一条使用Sequelize.js的路线

app.get('/api/users/:username', (req, res) => {
  const foundUser = getUserByUsername(req.params.username);
  console.log(`foundUser = ${foundUser}`);
  return res.send(foundUser);
});

getUserByUsername函数如下

const getUserByUsername = username => {
  Viewer.findOne({
    where: {username}
  }).then(response => {
    console.log(response.dataValues);//the object with the data I need
    return response.dataValues;
  });
};

我希望在我的路径中获取我的const foundUser中的对象，但似乎我需要等到findOne被执行，因为在我的控制台中我可以看到foundUser的日志（当时未定义）是在函数getUserByUsername

之前执行

foundUser = undefined
Executing (default): SELECT `id`, `username`, `instakluiten`, `role`, `createdAt`, `updatedAt` FROM `viewers` AS `viewer` WHERE `viewer`.`username` = 'instak' LIMIT 1;
{ id: 19,
  username: 'instak',
  instakluiten: 18550,
  role: 'moderators',
  createdAt: 2016-10-02T16:27:44.000Z,
  updatedAt: 2016-10-09T10:17:40.000Z }

如何确保在找到用户后，我的foundUser将使用数据进行更新？

Answer 1

app.get('/api/users/:username', (req, res) => {
getUserByUsername(req.params.username, function(err, result){
const foundUser = result;
console.log(`foundUser = ${foundUser}`);
 res.send(foundUser); 
});

});



const getUserByUsername = function(username, callback) {
Viewer.findOne({
where: {username}
}).then(response => {
console.log(response.dataValues);//the object with the data I need
return callback(null, response.dataValues);
});
};

Answer 2

您可以通过承诺或回调来避免它

app.get('/api/users/:username', (req, res) => {
  getUserByUsername(req.params.username, function(err, foundUser) {
    if (!err) {
      console.log(`foundUser = ${foundUser}`);
      return res.send(foundUser);
    } else {
      res.send(err)
    }
  });
});



const getUserByUsername = (username, callback) => {
  Viewer.findOne({
    where: {
      username
    }
  }).then(response => {
    console.log(response.dataValues); //the object with the data I need
    return callback(null, response.dataValues);
  });
};

Answer 3

你必须返回 Sequelize创建的承诺，然后等待它解决。所以getUserByUsername变为：

const getUserByUsername = username => {
  return Viewer.findOne({
    where: {username}
  }).then(response => {
    console.log(response.dataValues);//the object with the data I need
    return response.dataValues;
  });
};

并在路线中：

app.get('/api/users/:username', (req, res) => {
  getUserByUsername(req.params.username).then(foundUser => {
    res.send(foundUser);
  });
});

这是因为你需要保持承诺链。如果您忘记返回它，该函数将返回undefined结束，即使承诺得到最终解决，它解析的值也永远不会在链中回来。

如何等待执行findOne的续集

3 个答案: