Question

我有一个带有实例函数的类

// file1.js

export default class User {

constructor() {
this.userSchema = new Schema({
  username: String,
  password: String,
});
this.usermodel = Mongo.getModel('user', this.userSchema);
}

signUp({username, password}) {
var user = new this.usermodel({username: username,password: password});
this.usermodel.findOne({username: username}).exec((err, userresult) => {
  if (err) {
    /////////////// **LOCATION 1**: throw error that can be 
  } else {
    if(userresult) { // one user case so
      /////**LOCATION 2**: throw new Error("User with this Username already exists !. Please try a new Username.");
    } else { // null case
      return new DbResult({});
    }
  }
})
}

}

我称之为file1的signUp的另一个文件file2。

// file2.js

const user = new User();
try {
  user.signUp({username: request.body.username, password: request.body.password});
  console.log("reached means it is synchronous");
  response.status(200).json({'successmessage' : 'Successfully Signed Up'});
} catch (e) {
  response.status(400).json({'errormessage': e.message});
}

我想在位置1和2的file1.js中抛出错误，我想在file2.js（从中调用它）中捕获它，然后处理它。

有人可以帮忙怎么做？我对nodejs很新。

我读到了这样一个事实：我们不能像回调那样在回调中抛出错误，因为它只会使代码崩溃。我接下来也读到了这个，但我认为我没有理解它，所以不知道实际上要通过的地方。如果有人解释它并帮助我以正确的方式解决这个问题会很好。

Answer 1

如何使用promise承诺：

export default class User {

  constructor() {
    this.userSchema = new Schema({
      username: String,
      password: String,
    });
    this.usermodel = Mongo.getModel('user', this.userSchema);
  }

  signUp({username, password}) {
    var me = this;
    return new Promise(
      function(resolve,reject) {
        var user = new me.usermodel({username: username,password: password});
        me.usermodel.findOne({username: username}).exec((err, userresult) => {
          if (err) {
            reject(err);
          } else {
            if(userresult) { // one user case so
              reject(new Error(
                "User with me Username already exists !. Please try a new Username."
              ));
            } else { // null case
              resolve(new DbResult({}));
            }
          }
        })    
      }
    )
  }  
}

const user = new User();
user.signUp({username: request.body.username, password: request.body.password})
.then(//success
  function(result){
    //do something with result
    response.status(200).json({'successmessage' : 'Successfully Signed Up'});
  }
)
.then(//fail
  undefined //no success handler
  ,function(err){
    //do something with error
    response.status(400).json({'errormessage': e.message});
  }
);

节点js错误传播给调用者

1 个答案: