factory.rb

gistfile1.rb

class Account
  def self.create(params, provider)
    case provider
    when "facebook"
      Facebook.new(params)
    when "google_oauth2"
      Google.new(params)
    end
  end
end

# facebookのとき
account = Account.create(param,"facebook")
account.find_by_email_and_provider(email, provider) #この行がgoogleと同じになる

# googleのとき
account = Account.create(param,"google_oauth2")
account.find_by_email_and_provider(email, provider) #この行がfbと同じになる