如何控制针对异步操作的http请求

Question

我正在尝试在登录过程中获取用户数据。数据存储在 rethinkDb 中。流程是：

• 请求被路由到控制器（通过 express）

• 控制器选择正确的处理程序

• 处理程序调用 dao.get():

  login: function (email, password, res) {
        var feedback = daouser.get(email);
        if (feedback.success) {
            var user = feedback.data;
            //Do some validatios...
        }       
        res.status = 200;
        res.send(feedback);
    },

• dao.get() 代码为：

get: function (email) {        
    var feedback = new Feedback();
    self.app.dbUsers.filter({email: email}).run().then(function (result) {
        var user = result[0];
        feedback.success = true;
        feedback.data = user;
        return feedback;
    });
}

但由于调用是通过承诺进行的，因此调用实际“Then”函数之前的 dao.get return 并且控制器获得 undefined 反馈…

我的设计有问题…

Answer 1

var feedback = daouser.get(email);

您不能在这里进行同步赋值，因为 .get 是异步的。另外，请注意您没有从 .get 返回任何内容，这就是它未定义的原因。我会让所有这些成为承诺链。

get: function (email) {        
var feedback = new Feedback();

// RETURN is important here, this way .get() return a promise instead of undefined
return self.app.dbUsers.filter({email: email}).run().then(function (result) {
    var user = result[0];
    feedback.success = true;
    feedback.data = user;
    return feedback;
});

}

login: function (email, password, res) {
    //return the promise again, so login will be chainable too
    return daouser.get(email)
    // You can chain another then here, because you returned a promise from .get above
    // Your then function will be called with the return from the previous then, which is 'feedback'
    .then(function(feedback) {
      if (feedback.success) {
        var user = feedback.data;
        //Do some validatios...
      }       
      res.status = 200;
      res.send(feedback);
  }
},

如何控制针对异步操作的http请求

How to control http request that targets Async operation

node.js

express

promise

rethinkdb