Rails - .rubyテンプレートでCSVダウンロード ref: http://qiita.com/mnishiguchi/items/2e63dbe977cd278a4396

application.rb

require File.expand_path('../boot', __FILE__)

require 'csv'
require 'rails/all'

# ...

csv_helper.rb

module CsvHelper

  def set_file_headers(options)

    [:filename, :disposition].each do |arg|
      raise ArgumentError, ":#{arg} option required" if options[arg].nil?
    end

    disposition = options[:disposition]
    disposition += %(; filename="#{options[:filename]}") if options[:filename]

    headers.merge!(
      'Content-Disposition'       => disposition,
      'Content-Transfer-Encoding' => 'binary'
    )
  end
end

file0.txt

response.headers["Content-Disposition"] = 'attachment; filename="products.csv"'

CSV.generate do |csv|
  csv << ["Name", "Price", "URL"]
  @products.each do |product|
    csv << [
      product.name,
      number_to_currency(product.price),
      product_url(product)
    ]
  end
end

file4.txt

response.headers["Content-Disposition"] = 'attachment; filename="products.csv"'

CSV.generate do |csv|
  csv << ["Name", "Price", "URL"]
  @products.each do |product|
    csv << [
      product.name,
      number_to_currency(product.price),
      product_url(product)
    ]
  end
end

file5.txt

response.headers["Content-Disposition"] = 'attachment; filename="products.csv"'

CSV.generate do |csv|
  csv << ["Name", "Price", "URL"]
  @products.each do |product|
    csv << [
      product.name,
      number_to_currency(product.price),
      product_url(product)
    ]
  end
end

file6.txt

"<pre class=\"debug_dump\"><kbd style=\"color:brown\">&quot;id,username,sign_in_count,created_at,confirmed_at,updated_at\\n1,Masa Nishiguchi,2,2015-07-30 20:30:25 UTC,2015-07-30 20:30:24 UTC,2015-08-02 22:07:55 UTC\\n2,Elton Gottlieb,0,2015-07-30 20:30:25 UTC,2015-07-30 20:30:25 UTC,2015-07-30 20:30:25 UTC\\n3, (...中略...) ,Elroy Howe,1,2015-07-30 20:30:25 UTC,2015-07-30 20:30:25 UTC,2015-07-31 13:40:07 UTC\\n&quot;</kbd></pre>"

index.csv.ruby

# ==> 1. Set response headers
# http://api.rubyonrails.org/classes/ActionDispatch/Request.html#method-i-headers
set_file_headers filename:    "users-#{Date.today}.csv",
                 disposition: "attachment"

# ==> 2. Set options if you want (e.g. :col_sep, :headers, etc)
# http://ruby-doc.org/stdlib-2.0.0/libdoc/csv/rdoc/CSV.html#DEFAULT_OPTIONS
options = { headers: true }

# ==> 3. Generate csv that is to be downloaded

attributes = %w(id username sign_in_count created_at confirmed_at updated_at)

CSV.generate(options) do |csv|
  # Column names in a first row
  csv << attributes

  # Write each record as an array of strings
  @users.unscoped.each do |user|
    csv << attributes.map{ |attr| user.send(attr) }
  end
end

index.html.haml

= link_to "CSVダウンロード", users_path(format: "csv"), class: "btn btn-warning"

users_controller.rb

class UsersController < ApplicationController
  include CsvHelper
  # ...

  def index
    @users = User.all
  end

  # ...
end

users_controller_spec.rb

RSpec.describe UsersController, type: :controller do
  # ...

  describe "admin user" do
    before { log_in_as FactoryGirl.create(:admin), no_capybara: :true }

    describe 'GET #index' do

      before(:all) { 10.times { FactoryGirl.create(:user) } }

      it "renders the index page" do
        get :index
        expect(response).to render_template :index
      end

      describe "CSV format" do
        render_views  #<== 強制的にrspecにビューを生成させる

        before { get :index, format: "csv" }

        let(:user) { User.first}

        it { expect(response).to render_template :index }
        it { expect(response.headers["Content-Type"]).to include "text/csv" }

        attributes = %w(id username sign_in_count created_at confirmed_at updated_at)

        attributes.each do |field|
          it "has column name - #{field}" do
            expect(response.body).to include field
          end
        end

        attributes.each do |field|
          it "has correct value for #{field}" do
            expect(response.body).to include user[field].to_s
          end
        end

        it "has correct number of rows" do
          num_of_rows = 1 + User.all.count
          expect(response.body.split(/\n/).size).to eq num_of_rows
        end
      end
    end

    # ...
  end
end