$objectToArray

運算子 $objectToArray 可用來將檔 （object） 轉換成索引鍵/值組的陣列。 產生的陣列中的每個索引鍵/值組都會以具有 k 和 v 欄位的檔表示。 當您需要操作或分析集合內的文件結構時，此運算符很有用。

語法

{
  $objectToArray: <object>
}

參數

參數	Description
<object>	要轉換成索引鍵/值組陣列的檔 （object）。

範例

請參考商店集合中的此範例檔。

{
    "_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
    "name": "First Up Consultants | Beverage Shop - Satterfieldmouth",
    "location": {
        "lat": -89.2384,
        "lon": -46.4012
    },
    "staff": {
        "totalStaff": {
            "fullTime": 8,
            "partTime": 20
        }
    },
    "sales": {
        "totalSales": 75670,
        "salesByCategory": [
            {
                "categoryName": "Wine Accessories",
                "totalSales": 34440
            },
            {
                "categoryName": "Bitters",
                "totalSales": 39496
            },
            {
                "categoryName": "Rum",
                "totalSales": 1734
            }
        ]
    },
    "promotionEvents": [
        {
            "eventName": "Unbeatable Bargain Bash",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 6,
                    "Day": 23
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 7,
                    "Day": 2
                }
            },
            "discounts": [
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 7
                },
                {
                    "categoryName": "Bitters",
                    "discountPercentage": 15
                },
                {
                    "categoryName": "Brandy",
                    "discountPercentage": 8
                },
                {
                    "categoryName": "Sports Drinks",
                    "discountPercentage": 22
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 19
                }
            ]
        },
        {
            "eventName": "Steal of a Deal Days",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 21
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 29
                }
            },
            "discounts": [
                {
                    "categoryName": "Organic Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "White Wine",
                    "discountPercentage": 20
                },
                {
                    "categoryName": "Sparkling Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 17
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 23
                }
            ]
        }
    ]
}

範例 1：轉換 location 物件

此查詢會 location 將物件轉換成索引鍵值組的陣列。

db.stores.aggregate([
  {
    $project: {
      locationArray: { $objectToArray: "$location" }
    }
  },
  {
    $limit: 2  // Limit output to first 5 documents
  }
])

此查詢傳回的前兩個結果是：

[
  {
    "_id": "a715ab0f-4c6e-4e9d-a812-f2fab11ce0b6",
    "locationArray": [
      {
        "k": "lat",
        "v": -74.0427
      },
      {
        "k": "lon",
        "v": 160.8154
      }
    ]
  },
  {
    "_id": "923d2228-6a28-4856-ac9d-77c39eaf1800",
    "locationArray": [
      {
        "k": "lat",
        "v": 61.3945
      },
      {
        "k": "lon",
        "v": -3.6196
      }
    ]
  }
]

範例 2：轉換 salesByCategory 陣列

若要轉換 salesByCategory 陣列，請先展開陣列，然後套用 $objectToArray 運算子。

db.stores.aggregate([
  { $unwind: "$sales.salesByCategory" },
  {
    $project: {
      salesByCategoryArray: { $objectToArray: "$sales.salesByCategory" }
    }
  },
  { 
    $limit: 2
  }
])

此查詢傳回的前兩個結果是：

[
  {
    "_id": "a715ab0f-4c6e-4e9d-a812-f2fab11ce0b6",
    "salesByCategoryArray": [
      {
        "k": "categoryName",
        "v": "Stockings"
      },
      {
        "k": "totalSales",
        "v": 25731
      }
    ]
  },
  {
    "_id": "923d2228-6a28-4856-ac9d-77c39eaf1800",
    "salesByCategoryArray": [
      {
        "k": "categoryName",
        "v": "Lamps"
      },
      {
        "k": "totalSales",
        "v": 19880
      }
    ]
  }
]

當您想要動態處理功能變數名稱時，通常會使用將子檔轉換成索引鍵/值組，特別是在： - 建置泛型管線時。 - 將域名對應至索引鍵/值結構，以進行彈性轉換或進一步處理。

相關內容

• 檢視從 MongoDB 遷移到 Azure DocumentDB 的選項。
• 閱讀有關 與 MongoDB 的功能相容性的更多資訊。