Memoization in Rails controllers

Question

I'm working with Rails 4.0 and I want to eliminate some duplicate lines but I don't know the implications doing this in Rails. As I understand an instance of a controller is created in every request ¹.

class ResetController < ApplicationController
  def reset_password
    user = User.find_by_email(params[:email])
    if user
      ...
  end

  def reset_user_token
    user = User.find_by_email(params[:email])
    if user
      ...
  end
end

If I'm not using Rails, my idea is extract a private method using memoization and remove the duplicated lines:

private

def user
  @user ||= User.find_by_email(params[:email])
end

Is it a good idea do this in Rails controller? How do you improve this code? I have a similar problem in a lot of parts of the application.

Related:
- When to use memoization in Ruby on Rails
- Rails Best Practices: Use memoization

Answer 1

This seems not to have much to do with memoization, since as you say yourself, a new instance is started between those requests, so nothing would be 'stored'.

Still removing those duplicates in your code is a good idea. The Rails way to do this in your case would be a before_filter:

class ResetController < ApplicationController
  before_filter :find_user

  protected
  def find_user
    @user = User.find_by_email(params[:email])
    # here you could add some exception handling and prevent execution of action if no user is found (assuming you want to do this)
  end