CODEWITHSUNDEEP
swiftgoogle-cloud-firestoreswift5
GabrielB
GabrielB

Reputation: 153

How can I add these Firestore fields to a Dictionary?

I am looking to add all my "usernames" into a dictionary. I am having some trouble doing this. I am sure it's very obvious, but I am very new to coding.

I am stuck at, right now and can't seem to find a clear answer anywhere: 

func fetchUser() {
        let db = Firestore.firestore()
        let usernameSearch = db.collection("users")
        usernameSearch.getDocuments { (snapshot, error) in
            if error != nil {
                print("Error obtaining usernames")
            } else {
                for field in snapshot!.documents {
                   let field = field.get("username")
                    print(field!)
                }

            }

        }


}

I would really appreciate it if somebody could help me out. I am sure it's very obvious, or I'm just doing it totally wrong.

Upvotes: 0

Views: 393

Answers (2)

redmage1993
redmage1993

Reputation: 11

I'm assuming that what you're looking for is an Array, not a Dictionary. I'll also assume that you are indeed getting the correct value that you'd expect out of field.get("username"), e.g. a string such as "Bob." Therefore, what you are trying to do is map the list of document objects to a list of strings.

If you scroll to the Topics section of the Array documentation from Apple, you can find some of the operations they provide for arrays such as snapshot!.documents.

One of those operations is actually map, and its description is:

Returns an array containing the results of mapping the given closure over the sequence’s elements.

https://developer.apple.com/documentation/swift/array/3017522-map

In other words, you provide a transformation to perform for each instance of a document belonging to the snapshot!.documents Array and get back a new Array containing the resultant values of that transformation.

In this case I will use a more specific operation; compactMap. We have to try and cast the returned value from Any to String. If that does not succeed, it will return nil, and we'll want to filter that out. I expect it to be an unlikely case due to the type requirements made by the Firebase Console, but it's good to be aware of it. Here is the example:

func fetchUsernames(from usernameCollection: String, completion: @escaping ([String]) -> Void) {
    let db = Firestore.firestore()
    let collection = db.collection(usernameCollection)

    collection.getDocuments { snapshot, error in
        guard error != nil,
              let usernames = snapshot?.documents.compactMap { $0.get("username") as? String }
        else { return print("Error obtaining usernames") }
        
        completion(usernames)
    }
}

The key line here being let usernames = snapshot?.documents.compactMap { $0.get("username") }. We are passing the map function a closure. This closure is passed an argument itself; each value from the snapshot?.documents array. You may refer to this passed in value with $0.

Upvotes: 0

slushy
slushy

Reputation: 12385

First, get into the habit of safely unwrapping over force unwrapping. And choose more accurate names for your objects (i.e. usersCollection over usernameSearch). However, in this case, there's no need to instantiate individual properties for the database and the collection since they're not being used anywhere else but here (so be efficient and omit them).

var usersDictionary = [String: [String]]()

func fetchUser() {
    Firestore.firestore().collection("users").getDocuments { (snapshot, error) in
        if let snapshot = snapshot { // unwrap the snapshot safely
            var usernames = [String]()
            for doc in snapshot.documents {
                if let username = doc.get("username") as? String {
                    usernames.append(username)
                }
            }
            usersDictionary["usernames"] = usernames
        } else {
            if let error = error {
                print(error)
            }
        }
    }
}

Or if you actually meant an array of users:

var usersArray = [String]()

func fetchUser() {
    Firestore.firestore().collection("users").getDocuments { (snapshot, error) in
        if let snapshot = snapshot { // don't force unwrap with !
            for doc in snapshot.documents {
                if let username = doc.get("username") as? String {
                    usersArray.append(username)
                }
            }
        } else {
            if let error = error {
                print(error)
            }
        }
    }
}

Upvotes: 2

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