如何从存储在 Firestore (Swift) 中的文档返回对象

Question

I have a users collection in firebase and a user struct. I need to write a function that takes in the user's id and returns the corresponding user object:

struct AppUser: Codable {

    var id: String
    var displayName: String
    var photoURL: String
    var points: Int?
    var knownLanguageCodes: Set<String>?

}

This is my function that I have so far.

func getUser(id: String) -> AppUser? {

    let db = Firestore.firestore()
    let userRef = db.collection("users").document(id)

    userRef.getDocument { (document, error) in
         if let document = document, document.exists {
            let userID = document.data()?["id"] as! String
            let userDisplayName = document.data()?["displayName"] as! String
            let userPhotoURL = document.data()?["photoURL"] as! String
            let userPoints = document.data()?["points"] as! Int?
            let userKnownLanguageCodes = document.data()?["knownLanguageCode"] as! Set<String>?
            let user = AppUser(id: userID,
                               displayName: userDisplayName,
                               photoURL: userPhotoURL,
                               points: userPoints,
                               knownLanguageCodes: userKnownLanguageCodes)
            return user
         } else {
            print("Error getting user")
            return nil
        }
    }
}

Both of the return statements above give the error: Unexpected non-void return value in void function

I have looked at the code here https://cloud.google.com/firestore/docs/query-data/get-data under the heading 'Custom objects' and it doesn't seem to work for me. I get the error: Value of type 'NSObject' has no member 'data'. This is produced on line 6 of the code in the link.

Answer 1

You can't return inside a closure use a completion like

func getUser(id: String,completion:@escaping((AppUser?) -> ())) {

    let db = Firestore.firestore()
    let userRef = db.collection("users").document(id) 
    userRef.getDocument { (document, error) in
         if let document = document, document.exists {
            let userID = document.data()?["id"] as! String
            let userDisplayName = document.data()?["displayName"] as! String
            let userPhotoURL = document.data()?["photoURL"] as! String
            let userPoints = document.data()?["points"] as! Int?
            let userKnownLanguageCodes = document.data()?["knownLanguageCode"] as! Set<String>?
            let user = AppUser(id: userID,
                               displayName: userDisplayName,
                               photoURL: userPhotoURL,
                               points: userPoints,
                               knownLanguageCodes: userKnownLanguageCodes)
            completion(user)
         } else {
            print("Error getting user")
            completion(nil)
        }
    }
}

---

Call

getUser(id:<#str#>) { user in
  print(user)
}