Question

I am fairly new to Ruby on Rails and as a C# developer, when I want to re-use code (for a repository class), I could put it into a base class of type <T> to be able to do something like this:

public virtual IEnumerable<T> GetAll()
{
    return Context<T>.GetAll();
}

If I need to do any custom logic, I could, of course, override the method in my ‘User’ repository.

In Ruby, I am familiar that you can do this:

class UsersController < ApplicationController

This will allow access to all methods in ApplicationController and it’s parent classes. When using scaffolding, it generates the following method in each of my child classes:

def index
  @users = User.all

  respond_to do |format|
    format.html # index.html.erb
    format.xml  { render :xml => @users }
  end
end

What I end up with is 10 classes that have the same method, but the only difference is ‘User.all’, ‘Post.all’, etc.

How would I make this method generic so I can put it in my ApplicationController class?

Thanks for any assistance you can provide to a Ruby on Rails newbie.

Answer 1

The first thing to realize about the scaffolding code is that it can be abreviated, as such:

def index
  @users = User.all
end

unless you intend to deliver the view in another format, like json, html, pdf, the respond_to block is unnecessary. If you still feel the need to dry up this method, you could do something like

# app/controllers/concerns/autoload_records.rb

module AutoloadRecords
  included do
    before_action :load_records, only: :index
    before_action :load_record, only: [:create, :show, :edit, :update, :destroy]
  end

  private
  def load_records
    @records = model_class.all
  end

  def load_record
    @record = model_class.find(params[:id])
  end

  def model_class
    klass = self.class.to_s[/\A(\w+)sController\Z/,1] #=> get the name of the class from the controller Constant
    Object.const_get(klass)
  end
end

and write your controller like

class UsersController < ApplicationController
  include AutoloadRecords

  def index
    @records # => #<ActiveRecord::Relation[...]>
  end

  def show
    @record # => #<User ...>
  end

  def non_rest_action
    @record # => nil
    @records # => nil
  end
end