本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。

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

Amazon DocumentDB 中的`$isArray`運算子用於檢查文件中的欄位是否為陣列。此運算子在彙總管道和條件表達式中非常有用，可處理陣列類型欄位。

**參數**
+ `field`：要檢查是否為陣列的欄位路徑。

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

此範例示範如何使用 `$isArray`運算子來識別「庫存」欄位為陣列的文件。

**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": [{"location": "Mason City", "count": 250}, {"location": "Des Moines", "count": 1000}, {"location": "Ames", "count": 500}]}
]);
```

**查詢範例**

```
db.videos.aggregate([
  {
    $match: {
      $isArray: "$inventory"
    }
  },
  {
    $project: {
      _id: 1,
      name: 1,
      "inventory.location": 1,
      "inventory.count": 1
    }
  }
]).pretty();
```

**輸出**

```
{
  "_id": 4,
  "name": "Bravemind",
  "inventory": [
    {
      "location": "Mason City",
      "count": 250
    },
    {
      "location": "Des Moines",
      "count": 1000
    },
    {
      "location": "Ames",
      "count": 500
    }
  ]
}
```

## 程式碼範例
<a name="isArray-code"></a>

若要檢視使用 `$isArray`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 run() {
  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([
    {
      $match: {
        $isArray: '$inventory'
      }
    },
    {
      $project: {
        _id: 1,
        name: 1,
        "inventory.location": 1,
        "inventory.count": 1
      }
    }
  ]).toArray();

  console.log(result);

  await client.close();
}

run();
```

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

```
from pymongo import MongoClient

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([
    {
        '$match': {
            '$isArray': '$inventory'
        }
    },
    {
        '$project': {
            '_id': 1,
            'name': 1,
            'inventory.location': 1,
            'inventory.count': 1
        }
    }
]))

print(result)

client.close()
```

------