Convert Object array into String array

Question

How can I convert this object array into a string array? I'm reading records from a firebase collection.

    firebaseDB.collection("message").document(key).collection("messages").getDocuments() { (querySnapshot, err) in
        if let err = err {
            print("Error getting documents: \(err)")
        }
        else {
            self.driverArr.removeAll()
            for document in querySnapshot!.documents {
                print("\(document.documentID) => \(document.data())")
                let msgdata = document.data() as! [String:Any]
                var msgObj = Message()
                if let name = msgdata["name"] as? String {
                    msgObj.name = name
                }
                self.driverArr.append(msgObj)
            }
            if self.driverArr.count < 1 {
                print("No Drivers")
            }
            else{
                print("*** Driver Names array ***")
                print(self.driverArr)
            }
        }
    }

The current output of this array is:

[MainApp.Message(name: Optional("Oliver"), userId: Optional(""), msg: Optional(""), creatAt: Optional(0), latitude: Optional(""), longitude: Optional("")), MainApp.Message(name: Optional("Bluesona"), userId: Optional(""), msg: Optional(""), creatAt: Optional(0), latitude: Optional(""), longitude: Optional("")), MainApp.Message(name: Optional("Oliver"), userId: Optional(""), msg: Optional(""), creatAt: Optional(0), latitude: Optional(""), longitude: Optional(""))]

I wish to simply output an array that contains an Array of strings with the names ["Oliver", "Bluesona"...]

Try this if let name = msgdata["name"] as! String { msgObj.name = name } OR self.driverArr.append(msgObj!) — Naresh
– Naresh, Commented Oct 5, 2018 at 10:08

Rakesha Shastri · Accepted Answer · 2018-10-05 10:12:23Z

4

You can use compactMap to get all the valid names in the array.

print( driverArr.compactMap({$0.name}) )

answered Oct 5, 2018 at 10:12

Rakesha Shastri

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6 Comments

Denis Over a year ago

please let me know your answer and this code gives same result?

let arrNames = driverArr.map({ (doc: document) -> String in                 doc.name             })             print(arrNames)

Rakesha Shastri Over a year ago

No, first thing you are using map which doesn't filter out nil values. Second, driverArray is supposed to be of type Message since you are appending Message objects to it. let arr = driverArr.compactMap { (message) in message.name }

Denis Over a year ago

Thanks for reply but i want to confirm that both gives same result right?

Denis Over a year ago

Suppose if i have Object array that contains Int, String, Bool values and if i want to get only all int value as array then your .contactMap and .map works as same?

Denis Over a year ago

Okay, Thanks for your guide.

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