如何在 mongo 查询中动态使用 $push [重复]答案

【问题标题】：How to dynamically use $push in mongo query [duplicate]如何在 mongo 查询中动态使用 $push [重复]
【发布时间】：2017-05-25 20:46:57
【问题描述】：

我有一份格式如下的文件：

{ 
"Students" : {
    "Week1" : {
        "Monday" : [

        ], 
        "Tuesday" : [

        ], 
        "Wednesday" : [

        ], 
        "Thursday" : [

        ], 
        "Friday" : [

        ], 
        "Saturday" : [

        ], 
        "Sunday" : [

        ]
    }, 
    "Week2" : {
        "Sunday" : [

        ], 
        "Monday" : [

        ], 
        "Tuesday" : [

        ], 
        "Wednesday" : [

        ], 
        "Thursday" : [

        ], 
        "Friday" : [

        ], 
        "Saturday" : [

        ]
    }, 
    "Week3" : {
        "Sunday" : [

        ], 
        "Monday" : [

        ], 
        "Tuesday" : [

        ], 
        "Wednesday" : [

        ], 
        "Thursday" : [

        ], 
        "Friday" : [

        ], 
        "Saturday" : [

        ]
    }, 
    "Week4" : {
        "Sunday" : [

        ], 
        "Monday" : [

        ], 
        "Tuesday" : [

        ], 
        "Wednesday" : [

        ], 
        "Thursday" : [

        ], 
        "Friday" : [

        ], 
        "Saturday" : [

        ]
    }, 
    "Week5" : {
        "Sunday" : [

        ], 
        "Monday" : [

        ], 
        "Tuesday" : [

        ], 
        "Wednesday" : [

        ], 
        "Thursday" : [

        ], 
        "Friday" : [

        ], 
        "Saturday" : [

        ]
    }
  }
}

我想使用 Week1 作为变量动态地将一些元素推送到 Students.Week1.Monday。所以我想像这样构建它：

var dbNames = ['Zoe', 'Billy', 'Joey'];
var week = Week1; // week is dynamic entry
var query1 = {};
query1['Students.' + week + '.Monday'] = '$in: ' + dbNames;
Programs.update({ _id: teacherid }, { $push: query1 });

我搞砸了。任何帮助表示赞赏。

【问题讨论】：

标签： javascript mongodb meteor

【解决方案1】：

您可以动态创建对象来解决问题

var query = {};
var week = "DYNAMIC_VAL"; // Replace this
var day = "Monday";  // Dynamic Day
var dbNames = ['Zoe', 'Billy', 'Joey'];
query['Students'] = {};
query['Students'][week] = {};

// query['Students'][week][day] = { '$in': dBNames } // As per your query.
// but it should not work,
// if you want to push all elements of dbNames then you can use $each instead of $in

query['Students'][week][day] = { '$each': dBNames };


//console.log(JSON.stringify(query, null, 2));

Programs.update({ _id: teacherid }, { $push: query }, callback);

【讨论】：

我认为你不能在这里使用 $in，如果你想推送所有 dbNames 那么你需要使用 $each 而不是 $in
感谢您指出 $each 而不是 $in。我在想 $pull 运算符。您构建对象的方式给出了一个错误，声称它不能将 $push 应用于非数组。我构建对象的方法没有出错，但我错过了（你猜对了）对象的值应该是 { '$each': dbNames }。