How to Rewrite a Message to Include username

Question

I would like the username that created a record to be associated with that record. This ought to happen on the server and not via the originating client connection. The only place I see on the server to access the username is in canPerformAction. Is it possible to rewrite a message to insert the username before the record is created/updated in the storage connector? And even if I were to write my own storage connector, the username is not passed to the storage connector API. Can you give me any other options or guidance?

Answer 1

Usernames (as well as any other data) can be added to outgoing messages using dataTransform functions. Please find an in-depth explanation here:

http://deepstream.io/tutorials/transforming-data.html

Passing usernames to the storage connector is a bit trickier since there is no 1:1 relationship between a record and a user. If you'd like to create a private record I’d rather make the username part of the record name, e.g.

private-johndoe/iam7f3vy-2mgd656jrx3di

and use the permissionHandler’s canPerformAction method to make sure that all recordnames that start with ‘private-‘ continue with the name of the user that's interacting with them

canPerformAction: function( username, message, callback ) {
    if( message.topic === C.TOPIC.RECORD ) {
        var recordName = message.data[ 0 ];
        if( recordName.substring( 0, 8 ) === 'private-' ) {
            var providedUsername = recordName.substring( 8, recordName.indexOf( '/' ) );
            callback( null, providedUsername === username );
        }
    } else {
        callback( null, true );
    }
}