多次调用猫鼬模型的require [英] Call require on mongoose model more than once

问题描述

我的猫鼬模型定义如下:

I have models in mongoose defined as follows:

user.js

module.exports = function() {
  var mongoose = require('mongoose');

  // Creates a new Mongoose Schema object
  var Schema = mongoose.Schema; 

  // Collection to hold users
  var UserSchema = new Schema({
      username: { type: String, required: true },
      password: { type: String, required: true },
    },{ 
      versionKey: false 
    }
  );

  // Creates the Model for the User Schema
  var User = mongoose.model('User', UserSchema);

  var getUserById = function(id, callback) {
    User.findById(id, callback);
  }

  var getUserByUsername = function(username, callback) {
    var query = {username: username};
    User.findOne(query, callback);
  }


  return {
    getUserById: getUserById,
    getUserByUsername: getUserByUsername
  }
}()

基本上，我将返回用户模型的客户端可以使用的公共接口. IE.我的用户路线获取了模型，可以调用定义的两个公共方法，仅此而已.我这样做是为了从我的路线中提取出我正在使用mongodb/mongoose的事实.我很有可能会在某个时候也与Postgres对话的User模型，或者可能只是切换到Postgres.因此，我不想遍历代码中称为mongoose特定函数的地方方法.

Basically I am returning a public interface that clients of the User model can use. I.E. my routes for users grabs the model and can call the two public methods defined and nothing else. I am doing this to abstract the fact the I am using mongodb/mongoose from my routes. I will very likely have a User model that talks to postgres as well at some point, or may just switch to postgres. As such I don't want to have to look through the code for places in routes methods that called mongoose specific functions.

这是我的问题.在我需要调用模块的代码中的大多数地方

Here is my problem. Most everywhere in the code when I need a module I call

var someUtil = require('./someUtil');

但是，如果我对猫鼬模型执行多次以上操作，则会收到一条错误消息，指出无法对其进行两次定义.

However if I do that more than once for a mongoose model I get an error stating that it cannot be defined twice.

var User = require('./user');  // Cannot put this in more than one file without getting an error.

是否有更好的方法来编码user.js文件，以便我可以为我的User模型提供一个公共接口，但只定义一次Schema，以便我可以对该文件进行多次调用?

Is there a better way to code the user.js file such that I can provide a public interface to my User model but only define the Schema once so that I can call require more than one time on that file?

推荐答案

我也遇到了这个问题.

您可以做的就是将模式定义包装在try catch中

Something you can do is wrap the schema definition in a try catch

将此行var User = mongoose.model('User', UserSchema);替换为:

var User;
try {
  User = mongoose.model('User', UserSchema);
}
catch(e) {
  User = mongoose.model('User');
}

不确定它是否是最好的方法，但是它是否可以工作.

Not sure if its the best way but it will work.

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