DirtyInformation

Lethal Injection

When was the last time that you ran into something that just didn’t quite fit into the nice little RESTful world you think you’ve built yourself? Or when you found yourself jamming more and more conditionals into your controllers? Do you ever get the feeling there is just too much to be done in that little controller?

  #bad restful controller
  def update
    if params.has_key?(:ordered_ids)
      #update position attribute of each record
    else
      #some other form of updating
    end
  end

So you reach for the non-RESTful version.

  #routes.rb
  resources :things do
    collection do
      post :reorder
    end
  end

  #bad controller
  def reorder
    #update ordering
  end

This seems like it isn’t a bad idea at first, but then you start doing this all over the site. You find that your are copying code everywhere. All because you missed the noun. Why don’t we call is a sort order?

Now create a sort order controller for each thing needing sorting. Now we sit with a lot of rote work to set up each controller. We still haven’t reached the nirvana that we know is out there. All we need is a little dependency injection and the controllers can melt away.

I wish that I could claim that there is some amazing secret here, but Rails gives us a beautifully simple way to inject parameters into our controllers.

  #routes
  scope "things", as: "things", klass: Thing do
    resource :order, only: [:update]
  end
  resources :things

  scope "foos", as: "foos", klass: Foo do
    resource :order, only: [:update]
  end
  resources :foos

  #order controller
  def update
    SortOrder.new(sortable_class).reorder(ordered_ids)
    #...
  end

  private
  def sortable_class
    params.fetch(:klass)
  end

  def ordered_ids
    params.fetch(:ordered_ids) { [] }
  end

Ok, so what do we have going on here? I hope that no one gets hung up on the example and can see what is going on. Within the routes file we are injecting a parameter. In our case we happen to call it klass. You can call it whatever you like. This parameter need not be a String like the parameters coming from the browser. These parameters override anything coming from the browser and since we are using actual Ruby classes we have no issues with evaluating Strings.

Now we can reduce repetition and stay within the RESTful bounds. Our controllers really can concentrate on a single responsibility. Now I can get some sleep.

The Past

• Testing Named Agents 03 Feb 2017
• Two Duplication Refactorings in Elixir 18 Jan 2017
• B is for BigDecimal 24 Sep 2014
• A is for Abbrev 02 Sep 2014
• Missed Chances 15 Aug 2014
• Style Guides are Failures 15 Jun 2014
• What is BDD anyway? 15 Apr 2014
• An Agile Contract 31 Mar 2014
• What Do I Want 23 Mar 2014
• Just the Tip 16 Mar 2014
• Important Partnerships 11 Mar 2014
• Lost in Translation 03 Mar 2014
• Story Splitting Revisited 23 Feb 2014
• Let your yes be yes and your no be no 16 Feb 2014
• Lethal Injection 09 Feb 2014
• Smaller is Better 02 Feb 2014
• A Second Time 26 Jan 2014
• Introspective 20 Jan 2014
• Self Reflection for the Win 06 Dec 2013
• Why? Why? Why? 30 Sep 2013
• A New Gig 18 Sep 2013
• Exceptional Comments 15 Jun 2013
• Role Objects in Acceptance Tests 30 Apr 2013
• Open Closed Ruby Woes 28 Apr 2013
• Write Something 12 Apr 2013
• A Great Cast of Characters 06 Mar 2012
• When is the Release Party? 19 Aug 2011
• Single Responsibilty, How Did I Forget You 12 Apr 2011
• Change Classes not Styles 05 Nov 2010
• My MongoDB Cookbook Recipe 20 Jul 2010
• Agile Says What? 05 Nov 2009
• Inject & Me - BFFs 07 Sep 2008