Rails 3 Refactoring
Robert C. Martin (Agile Software Devlopment): SOLID
S: Single Resp Prin.
- Rails 0.x: ActionView::Base had too many responsibilities (details, templates, context, etc)
- Rails 1.0: Reduce responsibilities, separate classes out, (Template handlers (builder, rjs, haml, erb): single responsibility)
- Rails 2.2: view paths extracted (multiple places for view templates, allows Rails Engines)
- Rails 3.0: View paths split into 'view paths' and 'resolvers'
- Resolvers make it so views don't have to come from the filesystem (could be web service, database)
- Added lookup context too, so less back and forth between view and controller
Rails 3.1: AV::Renderer in from of ActionView -- only single responsibility per class
- Allows you to use something other than ActionView (e.g. Merb's views)
- Allows you to use the renderer in Sinatra
class BasicController <actionControlle::Base include ActionView::Context ...
Single reponsibilities: easier to separate out pieces and use them, and also replace them
- Easier to understand each piece
- Not as easy to take in the whole piece (top-down comprehension)
O: Open/closed Prin.
- Extend class behavior without modifying the class
Class open for etension, closed for modification
- Latter isn't enforced by Ruby
Don't break other people that depend on a library (e.g. modifying ActiveRecord::Base)
- Lots of poeple do --- makes it hard to run multiple rails apps on a single process
D: Dependency Inversion Prin.
"Depend on abstractions, not on concretions"
Duck typing, basically. Depend on abstractions (e.g. what methods are available), rather than a single concrete class.
match '/foo', to: 'posts#index' match '/foo', to: PostsController.action(:index) # Missed this last part, but it's a rack app!
Controllers have a middleware stack
- Remove hard-coded dependencies (e.g. pass as an optional parameter)
- Defining hooks (done in Railties)
L: Liskov Subs Prin.
"Derived classes must be substitutable for their base classes"
- Need to respond to the same interface
- What about a new version of Rails?
Static language: check to interface
include ActiveModel::Lint::Tests # kind of the same idea
I: Interface Seg. Prin
- Simplest protocol possible
- How to ensure?
- When you test, odn't use the conrete class -- use a Mock that only implements what you're expecting! (It's testing the 'concrete' interface, in a way)
Modularity driven by principles