Mongoose - 具有汇总结果的 foreach 循环答案

【问题标题】：Mongoose - foreach loop with aggregate resultMongoose - 具有汇总结果的 foreach 循环
【发布时间】：2016-09-10 18:40:33
【问题描述】：

我正在使用带有 mongoose 插件的 node.js 来构建带有任务的简单应用程序。我的 mongoDB 架构如下所示：

var userSchema = mongoose.Schema({

    username: String,
    email  : String,
    password : String,
    tasks: [{
      title: String,
      description: String,
      date: {type: Array, "default":[]}, 
      currentPeriod: Number,  
      periodQuantity: Number,
      done: Boolean
    }]

});

我想要做的是（例如）获取任务，其中“完成”变量设置为 true，并且是一个用户的一部分（同一文档）。目前，我的查询如下所示：

    User.aggregate({$match:{'email':req.user.email}},{$unwind:"$tasks"},{$match:{'tasks.done':true}},{$project:{'tasks':1,'_id':0}}, function(err,tasks){
      if (err) {
        console.log('Something went wrong during getting inactive task(s) for user "' + req.user.email + '": ' + err);
        res.send(err);
      }
      console.log('Succesfully got ' + tasks.length + ' inactive task(s) for user: "' + req.user.email + '".');
      res.json(tasks);
    });

问题是这样的查询结果是这样的

    [
    {"tasks":{"_id":"57372ef07329d9d8f2921ede","title":"Done1","description":"Done1Desc","currentPeriod":3,"periodQuantity":3,"done":true}},
    {"tasks":{"_id":"57372ef07329d9d8f2921edf","title":"Done2","description":"Done2Desc","currentPeriod":11,"periodQuantity":11,"done":true}},
    {"tasks":{"_id":"57372ef07329d9d8f2921ee3","title":"Done3","description":"Done3Desc","currentPeriod":3,"periodQuantity":3,"done":true}},
    {"tasks":{"_id":"57372ef07329d9d8f2921ee4","title":"Done4","description":"Done4Desc","currentPeriod":4,"periodQuantity":4,"done":true}}
    ]

虽然我只想要“属性”任务的值。我设法使用

在 mongo 控制台中获得了我感兴趣的结果

> var results = [];
> db.users.aggregate({$match:{'email':'admin'}},{$unwind:"$tasks"},{$match:{'tasks.done':true}},{$project:{'tasks':1,'_id':0}}).forEach(function(u) {results.push(u.tasks)})
> results
[
        {
                "_id" : ObjectId("57372ef07329d9d8f2921ede"),
                "title" : "Done1",
                "description" : "Done1Desc",
                "currentPeriod" : 3,
                "periodQuantity" : 3,
                "done" : true
        },
        {
                "_id" : ObjectId("57372ef07329d9d8f2921edf"),
                "title" : "Done2",
                "description" : "Done2Desc",
                "currentPeriod" : 11,
                "periodQuantity" : 11,
                "done" : true
        },
        {
                "_id" : ObjectId("57372ef07329d9d8f2921ee3"),
                "title" : "Done3",
                "description" : "Done3Desc",
                "currentPeriod" : 3,
                "periodQuantity" : 3,
                "done" : true
        },
        {
                "_id" : ObjectId("57372ef07329d9d8f2921ee4"),
                "title" : "Done4",
                "description" : "Done4Desc",
                "currentPeriod" : 4,
                "periodQuantity" : 4,
                "done" : true
        }
]
>

我尝试在 second 的 sn-p 结束时使用 foreach 和 each 函数，但是当我这样做时出现错误

TypeError: User.aggregate(...).forEach is not a function

【问题讨论】：

我也有同样的问题。 forEach 不是一个函数，显然 mongoose 没有那个特性。你解决这个？怎么样？
嗨，据我所知，我已经放弃了这种方法 - 但我也无法访问代码，所以我无能为力

标签： node.js mongodb mongoose mean-stack

【解决方案1】：

这可以使用$group 在聚合查询中完成。检查以下查询：

db.users.aggregate.aggregate([{
    $unwind: '$tasks'
}, {
    $match: {
        email: req.user.email,
        'tasks.done': true
    }
}, {
    $group: {
        _id: null,
        tasks: {
            $push: '$tasks'
        }
    }
}]);

【讨论】：