Question

This is a Noob question regarding Backbone.JS and ActiveRecord.
I’d be grateful for a pointer on how to debug this.

I’m trying to use Backbone.Js code to create a “Trainer” object, which has a single attribute, “name” (a string).
The front end of the application is Ruby on Rails. There is a data migration for the Trainer table.

In trainers controller:

def create
  document = Trainer.create! params[:trainer]
  render :json => document
end

Now, in app/assets/javascripts/backbone/views/trainers/new_view.js:

Gym.Views.Trainers.NewView = Backbone.View.extend({
  el : 'div.trainer_form',
  template: JST['backbone/templates/trainers/new_template'],
  model : new window.Gym.Models.Trainer({}),
  initialize: function() {
  this.document = this.options.user;
  Backbone.Validation.bind(this, {
    invalid: function(view, attr, error) {
      $("form#new-trainer .errors ul").append("<li>" + error + "</li>")
    }
  });
  this.render();
},
render : function() {

  $(this.el).html(this.template({trainer:this.model.toJSON()}));
  return this
},
events : {
  "click input#submit_button" : 'create_trainer'
},


create_trainer : function(event) {
  event.preventDefault()
  params = $("form#new-trainer").formParams()
  params['user_id'] = Gym.currentUser.userId
  this.model.save(params, {success : function(model, response) {
    Gym.trainers.add(model)
    Objects.views.selectTrainer.render()

    Gym.current_trainer = model

    $("select#trainer_selector").val(Gym.current_trainer.get('id'))

    Objects.views.new_trainer.model = new Gym.Models.Trainer()
    Objects.views.new_trainer.render()

  }
  });

Now, I can see in the Rails log that I’m getting to the controller:

Started POST "/trainers" ...
Processing by TrainersController#create as JSON
Parameters: {"name"=>"Lori Stevens", "user_id"=>1, "trainer"=>{}}

However, when it gets to the SQL, I see this:

[1m^[[36mSQL (0.4ms)^[[0m  ^[[1mINSERT INTO `trainers` (`created_at`, `name`, `updated_at`, `user_id`) VALUES ('2012-11-07 20:33:09', NULL, '2012-11-07 20:33:09', NULL)^[[0m

The parameter ‘name’ – which comes from the template, and is the attribute of the Trainer object- is not getting to the database, even though the parameter “name” is set in the JSON.

I’d appreciate a pointer on how to debug this – clearly I am not understanding how Backbone.js and ActiveRecord are connected.

Answer 1

The Controller takes the request from your browser and puts the data into ActiveRecord:

def create
  document = Trainer.create! params[:trainer]
  ...
end

But then you see request in the log, params[:trainer] equals the empty hash {}

You can either change the javascript that it creates json with a hash like

{ 'trainer': {'name' : 'Lori stevens', ... }}

I don’t know how easy this in backbone.

Or you can change your controller that it gets the values out of the hash and constructs an new hash for your trainer model, like it is:

gotten_name_from_json = params['name']
...
document = Trainer.create!(
   {:name => gotten_name_from_json, :town => gotten_twon_from_json})

I made this verbose to show that using this you can translate what ever json comes in, even when it comes from third parties where you can not control the format.