Realm Function & App Users

[Mauro]

Given a synced realm with the Email/Password authentication provider enabled, is it possible via a server function to search all app users by email address ?

[Andrew_Morgan]

Hi @Mauro - welcome to the MongoDB community forum!

How I’d handle this would be to have a User collection that contains a document for each registered user (chances are that you’ll want to store some extra data for each user anyway. You can optionally link the User collection to the Realm user through custom data (in which case, the user token contains a snapshot of that custom data – refreshed every time the user logs in).

You can auto-populate the User collection by setting up a Realm trigger that executes when a new user is registered:

This is the code from that trigger:

exports = function({user}) {
  const db = context.services.get("mongodb-atlas").db("RChat");
  const userCollection = db.collection("User");
  
  const partition = `user=${user.id}`;
  const defaultLocation = context.values.get("defaultLocation");
  const userPreferences = {
    displayName: ""
  };
  
  console.log(`user: ${JSON.stringify(user)}`);
  
  const userDoc = {
    _id: user.id,
    partition: partition,
    userName: user.data.email,
    userPreferences: userPreferences,
    location: context.values.get("defaultLocation"),
    lastSeenAt: null,
    presence:"Off-Line",
    conversations: []
  };
  
  return userCollection.insertOne(userDoc)
  .then(result => {
    console.log(`Added User document with _id: ${result.insertedId}`);
  }, error => {
    console.log(`Failed to insert User document: ${error}`);
  });
};

You then have to decide how you want the mobile app to access the data from the User collection:

1. If there’s nothing sensitive in the User collection then you could update the Realm Sync permissions to allow any user to open up a read-only synced realm for the User collection
2. You could use sync permissions and Realm rules to lock down the User collection, but then add a function (that you configure to run as the system user) that performs the search for you and then returns the results to the app.

This article describe a chat app I built that uses option 1. It describes the data architecture used and includes a link to the repo containing both the iOS (SwiftUI) and Realm apps.

[Mauro]

@Andrew_Morgan, thank you! Your solution works well.