Using Omnicontacts to get mail contacts from Google ref: http://qiita.com/vinhnguyenleasnet/items/53ade9f730d21a7a84d4

contact.html.erb

    <% unless @contacts.nil?%>
        <% @contacts.each do |c|%>
            <ul>
                <li><%= c[:name]%> :  <%= c[:email]%></li>
            </ul> 
        <%end%>
    <%end%>

file0.txt

    mkdir omnicontacts
    cd omnicontacts/
    rails new .

file1.rb

    gem 'omnicontacts'

file1.txt

    gem 'omnicontacts'

file2.rb

    class MainController < ApplicationController
        def index
        end
        def contact
        end
    end

file2.txt

    class MainController < ApplicationController
        def index
        end
        def contact
        end
    end

file3.rb

    require 'omnicontacts'

    Rails.application.middleware.use OmniContacts::Builder do
        importer :gmail, "client_id", "client_secret, {:redirect_path => "/oauth2callback", :ssl_ca_path => "/etc/ssl/certs/curl-ca-bundle.crt"}
    end

file3.txt

    require 'omnicontacts'

    Rails.application.middleware.use OmniContacts::Builder do
        importer :gmail, "client_id", "client_secret, {:redirect_path => "/oauth2callback", :ssl_ca_path => "/etc/ssl/certs/curl-ca-bundle.crt"}
    end

file4.rb

    Omnicontacts::Application.routes.draw do
        match "/contacts/:importer/callback" => "main#index", :via => [:get]
        match "/oauth2callback" => "main#contact", :via => [:get]
        # You can have the root of your site routed with "root"
        root 'main#index'
    end

file4.txt

    Omnicontacts::Application.routes.draw do
        match "/contacts/:importer/callback" => "main#index", :via => [:get]
        match "/oauth2callback" => "main#contact", :via => [:get]
        # You can have the root of your site routed with "root"
        root 'main#index'
    end

file5.rb

    class MainController < ApplicationController
        def index
        end
        def contact
            @contacts = request.env['omnicontacts.contacts']
            respond_to do |format|
                format.html 
            end
        end
    end

index.html.erb

    <h2>OmniContacts Example</h2>

    <a href="/contacts/gmail">Gmail</a>