Firebase Swift查询和客户端扇出

import Firebase

// 获取数据库引用
let ref = Database.database().reference()

// 创建一个查询，按 child("age") 排序，并且只获取 age 大于 18 的数据
let query = ref.child("users").queryOrdered(byChild: "age").queryStarting(atValue: 18)

// 监听查询结果
query.observe(.value, with: { snapshot in
    for child in snapshot.children {
        if let userSnapshot = child as? DataSnapshot,
           let user = userSnapshot.value as? [String: Any],
           let age = user["age"] as? Int {
            print("User age: \(age)")
        }
    }
})

func updateUserProfile(userId: String, profileData: [String: Any]) {
    let profileRef = ref.child("profiles").child(userId)
    let activityRef = ref.child("activities").child(userId)

    // 使用事务确保数据一致性
    profileRef.runTransactionBlock({ (currentData: MutableData) -> TransactionResult in
        // 更新用户资料
        currentData.value = profileData
        return TransactionResult.success(withValue: currentData)
    })

    // 直接更新用户活动列表（假设活动列表有一个字段指向用户资料）
    activityRef.child("profileUpdated").setValue(ServerValue.timestamp())
}

import Firebase

// 获取 Firestore 引用
let db = Firestore.firestore()

// 创建一个查询，按 "age" 字段升序排序，并且只获取 age 大于 18 的数据
let query = db.collection("users").order(by: "age").start(at: 18)

// 监听查询结果
query.addSnapshotListener { querySnapshot, error in
    guard let documents = querySnapshot?.documents else {
        print("Error fetching documents: \(error!)")
        return
    }
    for document in documents {
        if let age = document.get("age") as? Int {
            print("User age: \(age)")
        }
    }
}

func updateUserProfile(userId: String, profileData: [String: Any]) {
    let profileRef = db.collection("profiles").document(userId)
    let activityRef = db.collection("activities").document(userId)

    // 使用事务确保数据一致性
    db.runTransaction({ (transaction, errorPointer) -> Any? in
        // 更新用户资料
        transaction.setData(profileData, forDocument: profileRef)

        // 更新用户活动列表（假设活动列表有一个字段指向用户资料）
        transaction.setData(["profileUpdated": FieldValue.serverTimestamp()], forDocument: activityRef)

        return nil
    }) { object, error in
        if let error = error {
            print("Transaction failed. Error: \(error)")
        } else {
            print("Transaction successfully committed!")
        }
    }
}