我们如何让一个用户使用 Firebase/Firestore 注册另一个用户？

Question

I know it's possible to sign up a user with email and password with the following code:

FirebaseAuth.instance.createUserWithEmailAndPassword(
          email: email,
          password: password;)

That works fine. I can also add documents and collections in Firestore as such:

Future<void> getUserDoc() {
  // Initiate an auth instance
  final FirebaseAuth _auth = FirebaseAuth.instance;
  // Initiate a firebase firestore instance
  final FirebaseFirestore _firestore = FirebaseFirestore.instance;
  // Create a current user object
  User user = _auth.currentUser!;
  // Create a document reference based on the 'users'
  DocumentReference ref = _firestore.collection('users').doc(user.uid);

  // Return a collection that sets/updates the following data
  // based on the user.uid
  return ref.set({
    'UID': user.uid,
    'Email': user.email,
    'CreatedUserAt': user.metadata.creationTime,
    'LastSignInAt': user.metadata.lastSignInTime,
    'EmailVerified': user.emailVerified,
  });
}

What I need is that the user that is signed in now - for example a business, can sign up their clients. Their clients will receive a link in their email to confirm and then they are signed up to the platform. However, the tricky part is that those clients should be added to the business that signed them up through the business account when they log in. I'm really stuck with this part of how this logic would work in Firestore.

Answer 1

In my understanding, users with business account can invite client via an email and when the client signs up using the link, you need to add that client under this business. You can use a Cloud functions to invite a client along with business account ID of inviter as shown below:

exports.inviteClient = functions.https.onCall((data, context) => {
  // UID of user inviting client (or the business ID)
  const { uid } = context.auth; 

  // Add data in a database that maps user email with business ID
  // When user signs up, you can refer to this data to find who invited user

  // Send email link to sign up user

  return; 
});

After user signs up, you can then read ID of business who invited user and add it in users collection. I would recommend running this logic in a Cloud function so no user can change it from client side. Or if you'll use Firestore to store the mapping as well then you can use security rules to verify inviter ID.

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Another approach could be creating a user in inviteClient function itself and add a custom claim containing business ID.

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If you do not want to use Cloud functions then you can add a user document containing business ID right after someone is invited and use security rules to ensure users cannot change their inviter's ID. However, you'll need a Cloud function/server to generate sign in links for users and send emails.