Question

I am trying to get a better handle on Rail’s nested resources, and made a test app with models School and Class. In my routes.rb file, I have:

resources :schools do
   resources :classes
end

With the following models relationship for School and Class:

class School < ActiveRecord::Base
  attr_accessible: name
  has_many :classes
end

and

class Class < ActiveRecord::Base
  attr_accessible: name, school_id
  belongs_to :school
end 

I am having difficulty getting the school_id associated with the posts created under an URL like /schools/1/posts/new. More precisely, I would like to define a helper method like current_school that could take the first half of the URI where it contains the school_id, to allow me to write functions in the controller like current_school.posts.all that will automatically pull all the posts associated with school_id = what is in the URL. Thanks!

*Edit

Here is what I have in ClassController:

class ClassesController < ApplicationController

  def index
    @classes = current_school.classes.all
  end

  def new
    @class = current_school.classes.build
  end

  def create
    @class = current_school.classes.build(params[:post])
    if @class.save
      redirect_to root_path #this will be further modified once I figure out what to do
    else
      redirect_to 'new'
    end
  end

  private

  def current_school
    @current_school ||= School.find(params[:school_id])
  end

end 

And in the new.html.erb file:

  <div class="span6 offset3">
    <%= form_for([@school, @class]) do |f| %>

      <%= f.label :name, "class title" %>
      <%= f.text_field :name %>

      <%= f.submit "Create class", class: "btn btn-large btn-primary" %>
    <% end %>
  </div>

Answer 1

When you nest your resources, you get several helper methods for free as explained here. The method you’re looking for would be written as one of:

new_school_class_path(@school)
new_school_class_path(@school_id)

While your classes index page would be:

school_classes_path(@school)
school_classes_path(@school_id)

In your ClassesController, you would do something like:

def index
  @classes = current_school.classes
end

def new
  @class = current_school.classes.build
end

private
def current_school
  @current_school ||= School.find(params[:school_id])
end