so_callback_maybe_jquery.rb

class EmailSignupsController
  # jQuery style:
  def create
    AcceptsEmailSignupForm.call(params).then(method(:successful_signup)).fail(method(:failed_signup))
  end

  protected
  def successful_signup
    render 'email_signups/thank_you' and return
  end

  def failed_signup(errors)
    render('new', errors: errors) and return
  end
end

so_callback_maybe_lambdas.rb

class EmailSignupsController
  # lambda style:
  def create
    AcceptsEmailSignupForm.call(params, {
      success: ->{ render('email_signups/thank_you') },
      failure: ->(errors){ render('new', errors: errors) }
    })
  end
end

so_callback_maybe_methods_no_futures.rb

class EmailSignupsController
  # lambda style:
  def create
    AcceptsEmailSignupForm.call(params, {
      success: method(:successful_signup),
      failure: method(:failed_signup)
    })
  end

  protected
  def successful_signup
    render 'email_signups/thank_you' and return
  end

  def failed_signup(errors)
    render('new', errors: errors) and return
  end
end