Rails concerns, how to include a concern inside an api controller

Question

I am building a Rails api and currently have this folder structure:

The error_serializer.rb file is a module:

module ErrorSerializer
  extend ActiveSupport::Concern

  ...methods here...
end

Which I can include in any of the api controllers, for example:

class Api::TemplatesController < ApiController
  include ErrorSerializer
  ...
end

But since this errors_serializer module is only relevant to api controllers, I want to move the file to 'api/concerns/error_serializer.rb'.

But that generates the error:

ActionController::RoutingError (uninitialized constant Api::TemplatesController::ErrorSerializer)

I tried changing the name inside the file to:

module Api::ErrorSerialzer

but got the same error.

So what must I change to be able to move that file?

Did you change the include to be Api::ErrorSerializer?

Andrew Marshall
– Andrew Marshall

2017-10-07 16:26:21 +00:00
Commented Oct 7, 2017 at 16:26 — Andrew Marshall
– Andrew Marshall, Commented Oct 7, 2017 at 16:26
@AndrewMarshall Yes I did.

rmcsharry
– rmcsharry

2017-10-07 16:34:28 +00:00
Commented Oct 7, 2017 at 16:34 — rmcsharry
– rmcsharry, Commented Oct 7, 2017 at 16:34

jvillian · Accepted Answer · 2017-10-07 16:29:16Z

12

Since rails expects your module naming to follow your file structure, your concern should be named:

module Api::Concerns::ErrorSerializer

Since you're including it in Api::TemplatesController, I would do:

class Api::TemplatesController < ApiController
  include Api::Concerns::ErrorSerializer
  ...
end

To help rails out with the constant lookup.

answered Oct 7, 2017 at 16:29

jvillian

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Comments

rmcsharry · Accepted Answer · 2017-10-07 17:05:20Z

0

Thanks to the answer from @jvillian and this blog post, I was able to figure out the 'Rails' way to do this (since actually I will need the concern in all Api controllers, and also my api controller was outside the api namespace). So I'm posting this solution as (I think) it's the preferred way:

I moved the error_serialzier.rb file into api/concerns and change the code to include the Api namespace:

module Api::Concerns::ErrorSerializer
  extend ActiveSupport::Concern
  ...
end

I also moved api_controller.rb file and put it inside the /api folder, and thus into the API module namespace, so now it looks like this:

class Api::ApiController < ActionController::API
  before_action :authenticate_api_user!
  include DeviseTokenAuth::Concerns::SetUserByToken 
  include Concerns::ErrorSerializer

  respond_to :json
end

This got rid of the uninitialized constant errors.

answered Oct 7, 2017 at 17:05

rmcsharry

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4 Comments

Toshihiro Yokota Over a year ago

Do you know how to include error_serializer.rb if error_serializer.rb file is not in /api/concerns, but still in /concerns?

rmcsharry Over a year ago

@ToshihiroYokota I don't work in Rails any more, but try include Concerns::ErrorSerializer

Toshihiro Yokota Over a year ago

@rmcharry It just worked. I understand it works if I recognize "rails expects your module naming to follow your file structure". Thanks for that.

rmcsharry Over a year ago

@ToshihiroYokota Good to hear it worked, thanks for letting me know! :)

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