Swift + Firestore:如何获取相关对象

import Firebase
import FirebaseFirestore

// 在应用程序启动时初始化Firestore
FirebaseApp.configure()
let db = Firestore.firestore()

// 获取集合中的所有文档
db.collection("collectionName").getDocuments { (snapshot, error) in
    if let error = error {
        print("Error getting documents: \(error)")
    } else {
        for document in snapshot!.documents {
            let data = document.data()
            // 处理数据
        }
    }
}

// 监听文档变化
db.collection("collectionName").document("documentID").addSnapshotListener { (snapshot, error) in
    if let error = error {
        print("Error listening for document changes: \(error)")
    } else {
        if let data = snapshot?.data() {
            // 处理数据
        }
    }
}

// 获取特定文档
db.collection("collectionName").document("documentID").getDocument { (document, error) in
    if let document = document, document.exists {
        let data = document.data()
        // 处理数据
    } else {
        print("Document does not exist")
    }
}