How to catch validation error (422, Email already exists) in LoopbackJS?

Question

I use default Loopback's REST API. When I want to create a new user I just send a POST request to a default Loopback's endpoint /api/Users.

The issue is when an email already exists in a DB, Loopback throws an error ValidationError; status 422; Email already exists. And I don't know how to catch that error. Because if I use a default Loopback's endpoint, I cannot control User.create(...) method. It is called somewhere in the background throwing an error. And docs do not explain how to handle the error.

I can get rid of Loopback's default REST API and do all registration steps manually, like that:

User.create(..., function(err, user) {
    if(err) {
        handle error
    }
    handle success
})

But I'd like to use its default REST API, it is a framework after all. How can I catch and handle such an error?

Answer 1

I figured it out. They provide afterRemoteError() hook that runs after the remote method has finished with an error https://docs.strongloop.com/display/public/LB/Remote+hooks

User.afterRemoteError('create', function(ctx, next) {
    console.log('> Client.afterRemoteError triggered');
    console.error('ctx.error: ', ctx.error);
    next(err);
});