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# \$1arrayToObject
<a name="arrayToObject"></a>

Amazon DocumentDB 中的`$arrayToObject`運算子是`$objectToArray`運算子的反向。它需要一系列鍵值對文件，並將其轉換為單一文件。當您需要將一組鍵/值對轉換回物件或文件結構時，這特別有用。

**參數**
+ `array expression`：解析為陣列的表達式。陣列元素必須是具有兩個欄位的文件： `k`（索引鍵） 和 `v`（值）。

## 範例 (MongoDB Shell)
<a name="arrayToObject-examples"></a>

以下範例示範如何使用 `$arrayToObject`將鍵值對陣列轉換回文件。

**建立範例文件**

```
db.videos.insertMany([
  { "_id": 1, "name": "Live Soft", "inventory": { "Des Moines": 1000, "Ames": 500 } },
  { "_id": 2, "name": "Top Pilot", "inventory": { "Mason City": 250, "Des Moines": 1000 } },
  { "_id": 3, "name": "Romancing the Rock", "inventory": { "Mason City": 250, "Ames": 500 } },
  { "_id": 4, "name": "Bravemind", "inventory": { "Mason City": 250, "Des Moines": 1000, "Ames": 500 } }
]);
```

**查詢範例**

```
db.videos.aggregate([
  { $project: { name: 1, videos: { $objectToArray: "$inventory" } } },
  { $project: { name: 1, inventory: { $arrayToObject: "$videos" } } }
]);
```

**輸出**

```
{ "_id" : 1, "name" : "Live Soft", "inventory" : { "Des Moines" : 1000, "Ames" : 500 } }
{ "_id" : 2, "name" : "Top Pilot", "inventory" : { "Mason City" : 250, "Des Moines" : 1000 } }
{ "_id" : 3, "name" : "Romancing the Rock", "inventory" : { "Mason City" : 250, "Ames" : 500 } }
{ "_id" : 4, "name" : "Bravemind", "inventory" : { "Mason City" : 250, "Des Moines" : 1000, "Ames" : 500 } }
```

在此範例中，運算`$objectToArray`子用於將`inventory`物件轉換為金鑰/值對的陣列。然後，運算`$arrayToObject`子會用來將陣列轉換回文件，還原原始物件結構。

## 程式碼範例
<a name="arrayToObject-code"></a>

若要檢視使用 `$arrayToObject`命令的程式碼範例，請選擇您要使用的語言標籤：

------
#### [ Node.js ]

```
const { MongoClient } = require('mongodb');

async function example() {
  const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
  const db = client.db('test');
  const collection = db.collection('videos');

  const result = await collection.aggregate([
    { $project: { name: 1, videos: { $objectToArray: '$inventory' } } },
    { $project: { name: 1, inventory: { $arrayToObject: '$videos' } } }
  ]).toArray();

  console.log(result);
  await client.close();
}

example();
```

------
#### [ Python ]

```
from pymongo import MongoClient

def example():
    client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
    db = client['test']
    collection = db['videos']

    result = list(collection.aggregate([
        { '$project': { 'name': 1, 'videos': { '$objectToArray': '$inventory' } } },
        { '$project': { 'name': 1, 'inventory': { '$arrayToObject': '$videos' } } }
    ]))

    print(result)
    client.close()

example()
```

------