Using RABL (or other API builder) to handle model creation/update?

Question

I'm using RABL right now to generate JSON responses of an API in Rails, but I'm finding that while RABL is super handy for mapping models to responses, to create a consistent API I'm having to to duplicate that mapping logic in the update and create functions of my controller.

As a simple example, if I just want to change the attribute names in the response to a POST request, I can do this in RABL:

create.rabl

object @car
attributes car_id: :id, badly_named_legacy_column_that_means_color: :color

But if I want the client to be able to use these same "cleaned up" attributes in the JSON POST/PUT request itself (i.e. be able to send { "id": 1, "color": "red" } instead of { "car_id": 1, "badly_named_legacy_column_that_means_color": "red" }), I have to manually do this mapping again in the controller:

cars_controller.rb

def create
  params[:car_id] = params.delete(:id)
  params[:badly_named_legacy_column_that_means_color] = params.delete(:color)
  @car = Car.create(params)
end

Now there are two places that I need to map car_id to badly_named_legacy_column_that_means_color. Not very DRY.

So far I haven't come across any way to handle this using RABL. Is there one that I'm missing? I also realize this might be outside the scope of RABL, which bills itself specifically as a templating system, so maybe is there another API builder that would allow me to do this? I love the idea of mapping messy database columns to a clean API but having to specify this mapping in both the view and the controller isn't very DRY. Any thoughts appreciated.

score 1 · Accepted Answer · edited May 23 '17 at 10:25

1

Update

The original answer is all about Ruby/Rails => JSON, the question is JSON => Ruby/Rails. This answer about associating columns should explain an approach:

alias_attribute :new_column_name, :column_name_in_db

Then you can just reference new_column_name in the RABL and Rails will handle the association on the create/update.

You should be able to call render from the create method and render any view. You could customize a response with a create specific template or reuse the generic show template. The trick is to re-use the object rabl template (app/views/car/car.rabl in this case), for example:

  # POST /cars
  def create
    @car = Car.new(params)

    if @car.save
      render action: 'show'
    else
      respond_with @car
    end
  end

Where app/views/cars/car.rabl is

attributes :id, ...

and app/views/cars/show.rabl is

object @car

extends "cars/car"

edited May 23 '17 at 10:25

Community

1
1

answered Dec 13 '13 at 15:27

phillbaker

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Sorry if I wasn't clear, but this isn't what I'm asking - I'm not concerned with rendering the RESPONSE to the post, that I know how to do. I tweaked the question to draw more attention to the important part: that doing it the way I'm doing above results in TWO places I have to map DB column names to API property names, and I'd prefer to just do the mapping once. Ideally I could leverage the knowledge in the RABL template, but I'm open to other approaches. – Ryan Mitchell Dec 13 '13 at 18:25
Would putting the mapping in `car.rabl` work? You can just do the mapping once there and then reference that file from the different actions. It's basically a partial for the object. – phillbaker Dec 13 '13 at 19:13
The issue isn't duplicating the mapping in multiple RABL templates. It's duplicating the mapping in the template and the controller - having to perform database_column -> api_property in the template, and then to perform api_property -> database_column in the create action of the controller. – Ryan Mitchell Dec 13 '13 at 19:21
You're totally right. My answer is all about Ruby/Rails => JSON, your question is JSON => Ruby/Rails. This answer might help: http://stackoverflow.com/a/4017071/2284646. Or you can extract a class that does this mapping and centralizing the logic there. You're right, RABL is an output generator, not a parser. I'll update my answer. – phillbaker Dec 13 '13 at 20:00
Aliased attributes are an interesting idea - and if that isn't fine-grained enough it sounds like I'll need to suck it up and do it myself. Thanks for the help! – Ryan Mitchell Dec 15 '13 at 20:16

Using RABL (or other API builder) to handle model creation/update?

1 Answers1