app_controller.rb

class ApplicationController < ActionController::Base
  protect_from_forgery

  def current_search
    Search.find(session[:search_id])
  end

  def current_search?
    session[:search_id].present?
  end

  def source?
    params[:source_id].present?
  end

  def source
    Source.find(params[:source_id])
  end
end

mixes_controller.rb

class MixesController < ApplicationController
  respond_to :html, :json

  def index
    @mixes = mixes.published.page(params[:page]).per(50)

    respond_with @mixes
  end
  
  private

  def mixes
    if source?
      source.mixes
    elsif current_search?
      current_search.mixes
    else
      Mix
    end
  end
end

search.rb

class Search < ActiveRecord::Base
  
  def mixes
    mixes = Mix.published
    mixes = mixes.genre(genres) if genres.present?
    mixes.limit(50)
  end

end

searchs_controller.rb

class SearchesController < ApplicationController
  respond_to :html, :json

  def show
    @search = Search.find(params[:id])

    respond_with @search
  end

  def update
    @search = Search.find(params[:id])

    @search.update_attributes(params[:search])

    respond_with @search
  end

  def create
    @search = Search.create(params[:search])
    session[:search_id] = @search.id

    respond_with @search
  end

end

source.rb

class Source < ActiveRecord::Base
  has_many :mixes, :dependent => :destroy
end