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mongodb - 在 express (async/await) 中使用一个 mongoose 查询的输出作为另一个查询的输入

问题描述

我正在使用 express 和 mongoose 来实现服务器/数据库。我有一条工作路线，可以通过 playerID 获取所有涉及玩家的游戏。我现在正在尝试实现一个可以使用用户名而不是 playerID 的方法。

PLAYER_SCHEMA：

const mongoose = require('mongoose');

const PlayerSchema = mongoose.Schema( {
  username: {
    type:String,
    required:true,
    unique:true
  },
  date_registered: {
    type: Date,
    default:Date.now
  }
});

module.exports = mongoose.model('Player', PlayerSchema);

GAME_SCHEMA：

const mongoose = require('mongoose');

const GameSchema = mongoose.Schema( {
  player_1: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'Player',
    required: true
  },
  player_2: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'Player',
    required: true
  },
  status: {
    type:String,
  },
  hero_1: {
    type:String
  },
  hero_2: {
    type:String
  },
  date_registered: {
    type: Date,
    default:Date.now
  }

});

module.exports = mongoose.model('Game', GameSchema);

以下是我必须通过 playerId 查询所有涉及玩家的游戏：

//GET GAMES INVOLVING PLAYER BY PLAYER_ID
router.get('/player/:playerId', async (req, res) => {
  try {
    const games = await Game.find({$or:[{ player_1: req.params.playerId }, { player_2: req.params.playerId}]});
    console.log(games)
    res.json(games);
    // weird cuz doesn't throw error if not found, just returns empty list...
  }
  catch (err) {
    res.json({ message: err });
  }
});

以下概述了我想要做的事情，但它不起作用，因为我确信有很多原因：

我试图先从用户名中获取 userId，然后将其传递给游戏查询。

//GET ALL GAMES ASSOCIATED WITH PLAYER BY USERNAME
router.get('/username/:username', async (req, res) => {
  try {
    const player = await Player.findOne({username:req.params.username});
    console.log(player);
    const games =  Game.find({ $or:[{ player_1: player._id }, { player_2: player._id }] });
    res.json(games);
  }
  catch (err) {
    res.json({ message: err });
  }
});

我一直在阅读有关 .populate()、promise 和瀑布的内容，但我是新手，希望得到一些指导！

标签： mongodbexpressmongoosemongoose-schema

解决方案

请试试这个：

//GET ALL GAMES ASSOCIATED WITH PLAYER BY USERNAME
router.get('/username/:username', async (req, res) => {
    try {
        const player = await Player.findOne({ username: req.params.username });
        console.log(player);
        /**
         * .findOne() should return a document or null - if no match found..
         */
        if (player) {
            /**
             * .find() will return empty [] only if it didn't find any matching docs but won't throw an error in successful DB operation
             * (irrespective of whether docs matched or not, if op is successful then there will be no error).
             */
            const games = await Game.find({ $or: [{ player_1: player._id }, { player_2: player._id }] }).lean();
            (games.length) ? res.json(games) : res.json(`No games found for ${player._id}`);
        } else {
            res.json('No player found')
        }
    }
    catch (err) {
        res.json({ message: err });
    }
});

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