Mongoose 异步填充错误。没有正确调用方法

Question

所以我在搞乱猫鼬的种群。他们原来的example 太可怕了。它返回了错误：

TypeError: Cannot read property 'name' of undefined
at Promise.<anonymous> (/home/kevin/LearnMongoose/population/population-basic.js:104:56)
at Promise.<anonymous> (/home/kevin/node_modules/mongoose/node_modules/mpromise/lib/promise.js:162:8)
at Promise.EventEmitter.emit (events.js:94:17)
at Promise.emit (/home/kevin/node_modules/mongoose/node_modules/mpromise/lib/promise.js:79:38)
at Promise.fulfill (/home/kevin/node_modules/mongoose/node_modules/mpromise/lib/promise.js:92:20)
at Promise.resolve (/home/kevin/node_modules/mongoose/lib/promise.js:108:15)
at Promise.<anonymous> (/home/kevin/node_modules/mongoose/node_modules/mpromise/lib/promise.js:162:8)
at Promise.EventEmitter.emit (events.js:94:17)
at Promise.emit (/home/kevin/node_modules/mongoose/node_modules/mpromise/lib/promise.js:79:38)
at Promise.fulfill (/home/kevin/node_modules/mongoose/node_modules/mpromise/lib/promise.js:92:20)

我决定修改代码以使其正常工作。这就是新代码。

var mongoose = require('mongoose')
var Schema = mongoose.Schema;

console.log('Running mongoose version %s', mongoose.version);

/**
 * Console schema
 */

var consoleSchema = Schema({
    name: String
  , manufacturer: String
  , released: Date
})
var Console = mongoose.model('Console', consoleSchema);

/**
 * Game schema
 */

var gameSchema = Schema({
    name: String
  , developer: String
  , released: Date
  , consoles: [{ type: Schema.Types.ObjectId, ref: 'Console' }]
})
var Game = mongoose.model('Game', gameSchema);

/**
 * Connect to the console database on localhost with
 * the default port (27017)
 */

mongoose.connect('mongodb://localhost/bjank', function (err) {
  // if we failed to connect, abort
  if (err) throw err;

  // we connected ok
  createData();

})

/**
 * Data generation
 */

function createGame(){
  new Game({
     name: 'Legend of Zelda: Ocarina of Time'
      , developer: 'Nintendo'
      , released: new Date('November 21, 1998')
  }).save(function(err) {
      if(err) {
        console.log(err);
      } else {
        console.log('The Game has been saved');
      }

  });
}

function createConsole(){
  new Console({
     name: 'Nintendo 64'
    , manufacturer: 'Nintendo'
    , released: 'September 29, 1996'
  }).save(function(err) {
      if(err) {
        console.log(err);
      } else {
        console.log('The Console is saved');
      }

  });
}

  function pushToGame(){


    Game.findOne({name: /^Legend of Zelda/}, function (err, game){
      if(err) {return done(err);}
      console.log(game + '\n\n');
      Console.findOne({name: /^Nintendo 64/}, function  (err, consolee) {
        console.log('\n\nPulling specifed Game console\n');
        console.log(consolee);
        game.consoles.push(consolee);
        console.log('\n\nIt somehow works');
        console.log('\nThe second print of the game(should have the N64(consolee) console in the console ref array): \n\n' + game);

      })

    });
  }


  function showGame() {
    console.log('The method showGame() has started\n\n\n\n\n');
    Game.findOne({name: /^Legend of Zelda/}), function  (err, game) {
      console.log('This is not working');
      console.log(game);
  }

  }

function createData () {
  createGame();
  createConsole();
  pushToGame();
  showGame(); 

}


function done (err) {
  if (err) console.error(err);
  Console.remove(function () {
    Game.remove(function () {
      mongoose.disconnect();
    })
  })
}

在命令行中返回结果：

The method showGame() has started


{ name: 'Legend of Zelda: Ocarina of Time',
  developer: 'Nintendo',
  released: Sat Nov 21 1998 00:00:00 GMT-0500 (EST),
  _id: 5208628ddbc8cf1302000001,
  __v: 0,
  consoles: [] }


The Game has been saved
The Console is saved


Pulling specifed Game console

{ name: 'Nintendo 64',
  manufacturer: 'Nintendo',
  released: Sun Sep 29 1996 00:00:00 GMT-0400 (EDT),
  _id: 5208628ddbc8cf1302000002,
  __v: 0 }


It somehow works

The second print of the game(should have the N64(consolee) console in the console ref array): 

{ name: 'Legend of Zelda: Ocarina of Time',
  developer: 'Nintendo',
  released: Sat Nov 21 1998 00:00:00 GMT-0500 (EST),
  _id: 5208628ddbc8cf1302000001,
  __v: 0,
  consoles: [ 5208628ddbc8cf1302000002 ] }

当我进行一些修改时它并没有中断，但正如你所见，我放置了很多控制台日志来查看整个脚本中发生了什么。行：

方法 showGame() 已启动

应该在结尾而不是开头，因为这是我调用函数的顺序。

我不知道为什么这不起作用，因为它应该，但它不是。为什么我的 showGame() 函数在我创建数据之前就被调用了，即使它是在调用创建数据之后调用的？

其他信息

我对 Node.js 的结构有点了解。我知道它是异步工​​作的。也许 showGame 函数首先运行，因为前几个函数太慢了。如果是这种情况，我怎样才能让 showGame() 函数在这种结构中排在最后？

Answer 1

如果没有错误，您应该在前一个方法的回调之后调用每个函数，而不是使用createData() 方法。例如：

function createGame(){
  new Game({
     name: 'Legend of Zelda: Ocarina of Time'
      , developer: 'Nintendo'
      , released: new Date('November 21, 1998')
  }).save(function(err) {
      if(err) {
        console.log(err);
      }
      else {
        console.log('The Game has been saved');
        createConsole()
      }
  });
}

还有更冗长丑陋的解决方案：

function createData () {
  createGame(function(error) {
    if(error) {
        throw error;
    }
    else {
        createConsole(function(err) {
            if(err) {
                throw err;
            }
            else {
                pushToGame(function(er) {
                    if(er) {
                        throw er;
                    }
                    else {
                        showGame(function(e) {
                            if(e) {
                                throw e;
                            }
                            else {
                                // rest of your code
                            }
                        });
                    }
                });
            }
        });
    }
  });
}