javascript - 如何在 mongodb 中映射对象数组并将字符串值转换为数字？

Question

这里我有详细信息字段作为数组的文档:

 {   
        "_id" : ObjectId("60ae0b29ab282518443c7ac5"),
        "details": [
              {
                "label": "Asset title",
                "value": "S1",
              },
              {
                "label": "Total Cost",
                "value": "250",
              },
              {
                "label": "Possession Status",
                "value": "Available",
              },
              {
                "label": "Estimated Monthly Rent",
                "value": "15.5",
              }
            ]
    },
    {   
        "_id" : ObjectId("60ae0b29ab282518443c7ac8"),
        "details": [
              {
                "label": "Asset title",
                "value": "S2",
              },
              {
                "label": "Total Cost",
                "value": "455.5",
              },
              {
                "label": "Possession Status",
                "value": "Available",
              },
              {
                "label": "Estimated Monthly Rent",
                "value": "30",
              }
            ]
    }

因此，我尝试通过映射对象数组来 $project 这个对象数组，并检查标签是否为“总成本”或“估计月租金”，然后我想将它们转换为字符串值转为数字。例如: if {label = "Total Cost"} ，则: {"$toDouble": value} 并且 if {label = "Estimated Monthly Rent"} ，然后:{"$toDouble": value}

我正在尝试此操作，但出现错误。

 db.collection.aggregate([
       {
             "$project": {
                                   
                    "data": {
                         "$map": {
                                "input": "$details", 
                                 "as": "val", 
                                 "in": {
                                 "$cond":{ if: {"$$val.label": "Total Cost"} , then: { "$toDouble" : "$$val.value"}},
                                 "$cond":{ if: {"$$val.label": "Estimated Monthly Rent"} , then: { "$toDouble" : "$$val.value"}}
                                  }
                         }
                     } 
              }
        }
    ])

Answer 1

使用$in运算符检查条件，如果匹配则返回转换后的值，否则返回现有对象

db.collection.aggregate([
  {
    "$project": {
      "data": {
        "$map": {
          "input": "$details",
          "as": "val",
          "in": {
            $cond: [
              { $in: ["$$val.label", ["Total Cost", "Estimated Monthly Rent"]] },
              {
                label: "$$val.label",
                value: { $toDouble: "$$val.value" }
              },
              "$$val"
            ]
          }
        }
      }
    }
  }
])

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