使用猫鼬

Question

上午有我节点应用以下猫鼬架构

var expenseSchema = new Schema({ 
    particular : String, 
    date : {type : Date, default: Date.now}, 
    paid_by : String, 
    amount : Number, 
    month : String 
}); 

var roomSchema = new Schema({ 
    name: String, 
    admin: String, 
    roomies : [String], 
    expenses : [expenseSchema] 
},{ 
    collection : 'rooms' 
}); 

我需要费用一房一特定的月份使用find（）。 以下是我试图，但它返回我的整个房间对象

Room.findOne({_id : req.params._id, 'expenses.month' : 'oct'}).exec(function(err, result){ 
     if(result == null) { 
      res.json({result : 'Oops! We couldn\'t find any rooms...'});    
     } else if(err) { 
      res.json({result : 'Error in getting Rooms'}); 
     } else { 
      res.json({result : result}); 
     } 
    }); 

有人可以帮助我？

Answer 1

可以使用positional $ operator在projection在你的结果返回匹配的费用数组元素：

Room.findOne(
    { "_id": req.params._id, "expenses.month": "oct" }, 
    { "expenses.$": 1 } 
).exec(callback); 

或多个匹配，你可以使用聚合框架的$filter运营商在$project管道如：

var ObjectId = mongoose.Types.ObjectId; 
Room.aggregate() 
    .match({ "_id": new ObjectId(req.params._id), "expenses.month": "oct" }) 
    .project({ 
     "expenses": { 
      "$filter": { 
       "input": "$expenses", 
       "as": "item", 
       "cond": { "$eq": [ "$$item.month", "oct" ] } 
      } 
     } 
    }) 
    .exec(callback); 

或者如果您使用的是旧版本o不具备对MongoDB的3.2 $filter支持度f猫鼬的驱动程序，你可以使用$map一起$setDifference，在那里你可以在 “过滤器” 数组的内容，而无需使用$unwind：

var ObjectId = mongoose.Types.ObjectId; 
Room.aggregate([ 
    { "$match": { "_id": new ObjectId(req.params._id), "expenses.month": "oct" } },   
    { "$project": { 
     "expenses": { 
      "$setDifference": [ 
       { 
        "$map": { 
         "input": "$expenses", 
         "as": "items", 
         "in": { 
          "$cond": [ 
           { "$eq": [ "$$items.month", "oct" ] }, 
           "$$items", 
           false 
          ] 
         } 
        } 
       }, 
       [false] 
      ] 
     } 
    } } 
], function(err, results){   
    console.log(JSON.stringify(results[0], null, 4)); 
}); 

Answer 2

假设这可工作

var expenseSchema = new Schema({ 
    particular : String, 
    date : {type : Date, default: Date.now}, 
    paid_by : String, 
    amount : Number, 
    month : String 
}); 

var roomSchema = new Schema({ 
    name: String, 
    admin: String, 
    roomies : [String], 
    expense_id : type: Schema.Types.ObjectId, ref: 'expenseSchema' 
},{ 
    collection : 'rooms' 
}); 



Room.findOne({expense_id: req.params._id , "expenses.month": "oct" }) 
        .populate('expense_id') 
        .exec(function (err, doc) { 
         if (err) { 
          throw err 
         } 
         console.log(doc) 
         }) 

Answer 3

Room.findOne({ 
       _id : req.params._id, 
       'expenses.month':'oct' 
      },{ 
       'expenses': { 
       $elemMatch:{ 
        'month':'oct' 
       } 
       } 
      ).exec(
       function(err, result){ 
       if(result == null) { 
        res.json({result : 'Oops! We couldn\'t find any rooms...'});    
       } else if(err) { 
        res.json({result : 'Error in getting Rooms'}); 
       } else { 
        res.json({result : result}); 
       } 
      });