Rails pass value/object/orm from parent controller to child

Question

To keep to restfull protocol, I need to do /api/backup_jobs/777/errors .

In rails, the parent controller- I have:

module Api
  class BackupJobsController < ApplicationController
    respond_to :json

    def show
      @backup_job = @backup_jobs.find(params[:id])
      respond_with data: @backup_job
    end
  end
end

---

in the child controller:

module Api
  class ErrorsController < BackupJobsController
    respond_to :json

    def index
      respond_with data: @backup_jobs.find(params[:id]).backup_events.errors
    end
  end
end

But obvisouley this isn't going to work because params[] doesn't exist for /api/backup_jobs/777/errors

1. How can I pass the @backup_job = @backup_jobs.find(params[:id]) from the parent controller's def show to the child controller and have it accessible in the child's def index ?

Answer 1

You cannot do that because when an ErrorsController is created and used, you will not have a BackupsJobsController that ran before it.

This comes down to the nature of HTTP being a request-response protocol.

Instead, you can extract the line of code you wrote into a method that will be inherited by the ErrorsController.

backup_jobs_controller.rb :

module Api 
  class BackupJobsController < ApplicationController
    def show
      find_backup_job
      respond_with data: @backup_job
    end

  protected

    def find_backup_job
      @backup_job = @backup_jobs.find(params[:id])
      # or maybe @backup_job = BackupJob.find(params[:id])
    end

  end
end

errors_controller.rb :

module Api
  class ErrorsController < BackupJobsController
    respond_to :json

    def index
      respond_with data: find_backup_job.backup_events.errors
    end
  protected

    def find_backup_job
      @backup_job = BackupJob.find(params[:backup_job_id])
    end

  end
end