Swift:将来自Firestore子集合的uid=uid的数据存储到对象中

Question

所以我试图将从Firestore数据库检索到的数据存储到一个对象中。我的数据库有一个用户集合，每个用户都有一个类集合。我希望能够获得已登录用户的类集合，并将它们存储在对象数组中。到目前为止，我尝试过的大多数方法都可以提取数据，但它不会将其保存到任何东西中，因为它可以从完成处理程序中访问数据。任何帮助都会很棒，这是我正在使用的代码rn:

db.collection("users").whereField("uid", isEqualTo: uid).addSnapshotListener { (querySnapshot, error) in
if error == nil && querySnapshot != nil {
let docId = querySnapshot?.documents[0].documentID
db.collection("users").document(docId!).collection("classes").addSnapshotListener { (querySnap, error) in
guard let documents = querySnap?.documents else{print("No Classes");return}
var imageData:UIImage?
retrievedClasses = documents.map { (querySnap) -> UserClass in
let data = querySnap.data()
if let decodedData = Data(base64Encoded: data["class_img"] as! String, options: .ignoreUnknownCharacters){
imageData = UIImage(data: decodedData)
}
return UserClass.init(name: data["class_name"] as! String, desc: data["class_desc"] as! String, img: imageData!, color: data["class_color"] as! String, link: data["class_link"] as! String, location: data["class_location"] as! GeoPoint, meetingTime: data["meeting_time"] as! Dictionary<String,String>)

}
print(retrievedClasses[0].printClass())
}
}
}

Answer 1

据我所知，你需要做这样的事情：

func getUserClasses(for userID: String, completion: @escaping (Result<[UserClass], Error>) -> Void) {
db.collection("users").whereField("uid", isEqualTo: userID).addSnapshotListener { (querySnapshot, error) in
if error == nil && querySnapshot != nil {
let docId = querySnapshot?.documents[0].documentID
db.collection("users").document(docId!).collection("classes").addSnapshotListener { (querySnap, error) in
guard let documents = querySnap?.documents else {
print("No Classes")
completion(.failure("No Classes"))
return
}
let retrievedClasses = documents.map { (querySnap) -> UserClass in
let data = querySnap.data()
var imageData: UIImage?
if let decodedData = Data(base64Encoded: data["class_img"] as! String,
options: .ignoreUnknownCharacters) {
imageData = UIImage(data: decodedData)
}
let user = UserClass(name: data["class_name"] as! String,
desc: data["class_desc"] as! String,
img: imageData!,
color: data["class_color"] as! String,
link: data["class_link"] as! String,
location: data["class_location"] as! GeoPoint,
meetingTime: data["meeting_time"] as! Dictionary<String,String>)
return user
}
completion(.success(retrievedClasses))
}
} else {
completion(.failure("Request Error"))
}
}
}

然后您将能够在请求完成后使用数据：

getUserClasses(for: "123") { result in
switch result {
case .success(let allClasses):
retrievedClasses = allClasses // retrievedClasses is a property in your class which you are going to use  
if !retrievedClasses.isEmpty() {
print(retrievedClasses[0].printClass())
}
case .failure(let error):
print(error)
}
}