Memoized helper methods instead of instance variables in controllers

pdbradley · March 22, 2016, 11:38am

This is sort of a personal question to @sgrif but might be of general interest so I’m posting it here. I recently discovered the Bikeshed podcast and have been going through the episodes (starting with number 1). On at least two separate episodes Sean has said rather contentedly that he doesn’t like to pass instance variables to views, he prefers to use memoized helper methods. I know what memoized means and I know what helper methods are, but I’m not sure where you would put those methods, or how they would look.

Anyway I’d love to see an example of what you are talking about because I agree with the general philosophy of what you are saying.

I love the podcast.

davidcpell · March 22, 2016, 2:39pm

Here’s a gist that gives an example of using memoized helper methods in a controller:

gist.github.com

https://gist.github.com/bloudermilk/8345597

memoized-helper-methods.md

Last year I started playing around with using memoized private helper methods in my controllers instead of the traditional instance variable assigns we see in RoR controllers. Here's an example:

```ruby
class PostsController < ApplicationController
  helper_method :new_post, :post, :posts
  
  def new; end
  def show; end
  def edit; end
  def index; end

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It turns out ActionController has a helper_method class method that makes methods available in the views as if they were defined in an actual helper module:
http://apidock.com/rails/ActionController/Helpers/ClassMethods/helper_method

You can memoize the results of private methods in the controller and then make those methods available to the view as helper methods.

pdbradley · March 22, 2016, 5:01pm

That’s super helpful @davidcpell, thanks!

andyw8 · March 22, 2016, 7:17pm

I agree with avoiding instance variables in views.

I tried the memoized variables approach for a while, but I’ve come to prefer explicit render calls instead. Here’s an example:

gist.github.com

https://gist.github.com/andyw8/f765fcf47244d25d0dce

renders.rb

class WidgetsController < ApplicationController
  def index
    render 'index', locals: { widgets: scoped_widgets }
  end

  def show
    render 'show', locals: { widget: find_widget }
  end

  def new

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Memoized helper methods instead of instance variables in controllers

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