Capture username to write in new post - ios

Question

When a user signs in, their UID is set to standardUserDefaults(). Also, the users' profile data is saved under a child named their uid.
When the user creates a post, I would like to attach their username/display name to the post.
I've set up a function to fetch the current user's username, but whenever I submit a post, it seems as though the closure is not being executed.
The post model:
class PostModel {
var postBody = String()
var creationDate = String()
var postUID = String()
var userName = String()
init(postBody: String) {
self.postBody = postBody
let dateObject = NSDate()
let formatDate = timeToString(dateObject)
self.creationDate = formatDate
let userID = NSUserDefaults.standardUserDefaults().valueForKey("uid") as! String
self.postUID = userID
self.userName = getUsername(userID)
}
// Used to convert the model to json compatible before saving
func postToDictionary() -> NSDictionary {
let jsonBody = postBody
let jsonDate = creationDate
let jsonUID = postUID
let jsonUsername = userName
let postAsDictionary = ["Body": jsonBody, "Timestamp": jsonDate, "UID": jsonUID, "Display Name": jsonUsername]
return postAsDictionary
}
}
and the function to get the username:
func getUsername(withUID: String) -> String {
var userName = String()
DataService.ref.userRef.childByAppendingPath(withUID).observeSingleEventOfType(.Value, withBlock: { snapshot in
userName = snapshot.value.objectForKey("Display Name") as! String
})
return userName
}

Answer 1

I set up my login function to get the current user's display name and set it to the standardUserDefaults which worked. I believe this is my solution unless someone has a better suggestion
#IBAction func loginButton(sender: AnyObject) {
if emailField != nil && passwordField != nil {
let emailAttempt = emailField.text!
let passwordAttempt = passwordField.text!
DataService.ref.baseRef.authUser(emailAttempt, password: passwordAttempt) {
error, authData in
if error != nil {
print("error in data check")
} else {
let returnUID = authData.uid
NSUserDefaults.standardUserDefaults().setValue(returnUID , forKey: "uid")
DataService.ref.userRef.childByAppendingPath(returnUID).childByAppendingPath("Display Name").observeSingleEventOfType(.Value, withBlock: { snapshot in
let UserDisplayName = snapshot.value as! String
NSUserDefaults.standardUserDefaults().setValue(UserDisplayName, forKey: "displayName")
self.performSegueWithIdentifier("loginSuccessSegue", sender: sender)
})
}
}
} else {
print("error")
return
}
}