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$toBool
Amazon DocumentDB 中的$toBool运算符将表达式转换为布尔值。
参数
注意：任何字符串都将转换为true。
示例（MongoDB 外壳）
以下示例演示如何使用$toBool运算符对来自不同数据类型的设备状态值进行标准化。
创建示例文档
db.deviceStates.insertMany([
{ _id: 1, deviceId: "sensor-001", status: true },
{ _id: 2, deviceId: "camera-002", status: 1 },
{ _id: 3, deviceId: "thermostat-003", status: "active" },
{ _id: 4, deviceId: "doorlock-004", status: 0 }
]);
查询示例
db.deviceStates.aggregate([
{
$project: {
_id: 1,
deviceId: 1,
isActive: { $toBool: "$status" }
}
}
]);
输出
[
{ "_id": 1, "deviceId": "sensor-001", "isActive": true },
{ "_id": 2, "deviceId": "camera-002", "isActive": true },
{ "_id": 3, "deviceId": "thermostat-003", "isActive": true },
{ "_id": 4, "deviceId": "doorlock-004", "isActive": false }
]
代码示例
要查看使用该$toBool命令的代码示例，请选择要使用的语言的选项卡：
- Node.js
-
const { MongoClient } = require('mongodb');
async function main() {
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('deviceStates');
const result = await collection.aggregate([
{
$project: {
_id: 1,
deviceId: 1,
isActive: { $toBool: '$status' }
}
}
]).toArray();
console.log(result);
await client.close();
}
main();
- Python
-
from pymongo import MongoClient
def main():
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['deviceStates']
result = list(collection.aggregate([
{
'$project': {
'_id': 1,
'deviceId': 1,
'isActive': { '$toBool': '$status' }
}
}
]))
print(result)
client.close()
if __name__ == '__main__':
main()
