How prevent username from duplicate signUp in Firebase? [duplicate] - ios

Question

This question already has answers here:
Firebase android : make username unique
(4 answers)
Closed 6 years ago.
I want to prevent duplicate username while signUp form what user entered. I have created email login like below, firtly createUser and then auth it setValue with user dictionary.
But I stack with Firebase security settings and how to check handle this situation.
REF_BASE.createUser(email, password: pwd, withValueCompletionBlock: { ..
REF_BASE.authUser(email, password: pwd, withCompletionBlock: { ..
REF_USERS.childByAppendingPath(uid).setValue(user)
This handling always response error.
REF_USERS.childByAppendingPath(uid).childByAppendingPath("username").setValue(user["username"]) { (error: NSError!, result: Firebase!) in
if error != nil {
print(error.localizedDescription)
}
else {
self.REF_USERS.childByAppendingPath(uid).setValue(user)
}
}
This is my security rules, How Can I fix everything to be prevented from duplicate user?
"users": {
".read": "auth !== null",
"$user": {
"username": {
".read": "auth !== null",
".write": "newData.val() === auth.uid && !data.exists()"
}
}
},
Update:
From Frank's answer, but I don't know what I need to do while signUp new user for swift in this situation.
app : {
users: {
"some-user-uid": {
email: "test#test.com"
username: "myname"
}
},
usernames: {
"myname": "some-user-uid"
}
}
Need I add same user uid at the same time for two different nodes? If someone explain it in Swift. It would be great.
"users": {
"$uid": {
".write": "auth !== null && auth.uid === $uid",
".read": "auth !== null && auth.provider === 'password'",
"username": {
".validate": "
!root.child('usernames').child(newData.val()).exists() ||
root.child('usernames').child(newData.val()).val() == $uid"
}
}
}
I couldn't add new user informations to usernames parent node. It's needed another security rules?

Answer 1

If you are trying to prevent duplicate Firebase usernames, that can be done right at the createUser stage.
Assume a dialog is presented to new user asking to create an account: this will get their desired userName and password.
Send that to createUser and if there's an error (because it already exists) notify them and ask for a different userName:
myRootRef.createUser(email, password: pw, withValueCompletionBlock: { error, result in
if error != nil {
self.errMsgField.stringValue = "email/username in use, try again"
} else {
let uid = result["uid"] as! String //the uid of the new user
print("user created as \(uid)")
self.authUserWithAuthData( email, password: pw ) //auth the user
}
})
After the user is created you would probably add their info the /users node as well.