Calling setValuesForKeys fails in my Swift 4 code

Question

I'm having this problem, im trying to retrieve data from the firebase database, but it's saying the profilepic isn't a key, but it is. This is the object class.

class User: NSObject {
    var firstname: String?
    var lastname: String?
    var username: String?
    var profilepic: String?
}

and this is me trying to retrieve

func getusers(){
        ref.child("Friends").child(currentuser!).observe(.childAdded, with: { (snapshot) in
            print(snapshot)
            if let dic = snapshot.value as? [String: AnyObject]{
                let user = User()
                user.setValuesForKeys(dic)
                print(user.firstname, user.lastname)

                DispatchQueue.main.async {
                    self.tableview.reloadData()
                }}
        }) { (error) in
            print(error.localizedDescription)
        }

    }

and the crash is here user.setValuesForKeys(dic) .

Anyone has any idea why isn't working?

Answer 1

Try this instead:

@objcMembers
class User: NSObject {
    ...
}

The setValuesForKeys API is implemented by the Foundation framework and requires Objective-C compatibility.

The rules for exposing Swift code to Objective-C have changed considerably in Swift 4. Please check the evolution proposal for further information.

User class design . If any of the four properties can be missing from Firebase than your class design might be a good fit. Otherwise, consider declaring the fixed properties as non-optional and creating an initializer instead.

Answer 2

Change your User declaration to this:

class User: NSObject {
    @objc var firstname: String?
    @objc var lastname: String?
    @objc var username: String?
    @objc var profilepic: String?
}

In Swift 4, Objective-C cannot see your instance properties unless you expose them explicitly.