LoopBack: How to change a remote method to handle both callbacks and promise based invocations?

README.MD

You can use the following link to see a diff of how I added callbacks AND promise support to MyModel.js file:

https://gist.github.com/pulkitsinghal/dc8fa7c5c7b71fef5542/revisions?diff=split#diff-31bccba1284da099d610b2e5c437debf

MyModel.js

var loopbackUtils = require('loopback/lib/utils'); // handle both callbacks and promise based invocations

module.exports = function(MyModel) {

  MyModel.remoteMethod('generateToken', {
    accepts: [
      {arg: 'id', type: 'string', required: true}
    ],
    http: {path: '/:id/generateToken', verb: 'get'}
  });

  MyModel.generateToken = function(id, cb) {
    log('inside generateToken');

    cb = cb || loopbackUtils.createPromiseCallback(); // handle both callbacks and promise based invocations

    MyModel.app.models.AccessToken.createAccessTokenId(function(err, token){
      if (err){
        log('inside generateToken', 'ERROR', err);
        cb(err);
      }
      else {
        log('inside generateToken', 'token:', token);

        MyModel.updateAll(
          {id: id},
          { token : token },
          function(err) {
            if (err){
              log('inside generateToken', 'ERROR', err);
              cb(err);
            }
            else {
              log('inside generateToken', 'saved token in MyModel');
              cb(null);
            }
          }
        );
      }
    });

    return cb.promise; // handle both callbacks and promise based invocations
  };

};