Page 0: Page 1: Refactoring Your Rails Application RailsConf 2008 Zach Dennis Mutually Human Software www.mutuallyhuman.com Drew Colthorp Atomic Object www.atomicobject.com Page 2: Example Extract Query to Model Page 3: What is refactoring? Page 4: Why refactor? Page 5: Why refactor? Program Evolution Page 6: Why refactor? Technical Debt / Pain Management Page 7: How do you refactor? Page 8: How do you refactor? Step #1 - have solid tests Page 9: How do you refactor? Short deliberate steps Page 10: How do you refactor? Wear two hats, but only one at a time. Page 11: Testing Automated test suite preferred Page 12: Testing When in doubt nothing beats a good manual test plan Page 13: What do you refactor? Page 14: What do you refactor? Code that smells Page 15: Common smells in Rails apps Duplicated Code Shotgun Surgery Long Method Inappropriate Intimacy Divergent Change Large Class Feature Envy Message Chains Comments Page 16: Duplicated Code smell def organizer_names Organizer.find(:all).map(&:name) end def organizer_ids Organizer.find(:all).map(&:id) end Page 17: Shotgun Surgery smell A change requires modifying many different parts of your application. Page 18: Long Method smell 1: def create 2: @record = Record.find(params[:id]) 3: @record.name = params[:name] ... 37: if @record.save 38: redirect_to records_path 39: else 40: render :action => “edit” 41: end 42:end Page 19: Inappropriate Intimacy smell class PeopleController def index Person.find(:all, :select => “name”, :include => [:companies, :groups] :order => :updated_at ) end end Page 20: Divergent Change smell A class is commonly changing in different ways for different reasons. Page 21: Large Class smell A class is doing too much. Common indicators: - too many instance variables - too much code Page 22: Feature Envy smell A method is more interested in a class other than the one it is actually on. Page 23: Many more smells exist http://www.refactoring.com/sources.html Page 24: Deliberate code smells Code smells have their tradeoffs Page 25: When do you refactor? Page 26: When do you refactor? Adding a feature Page 27: When do you refactor? Cleaning up the code base Page 28: When do you refactor? Spikes, prototyping Page 29: Refactoring is essential Red. Green. Refactor. Page 30: Common Rails Dilemma MVC paralysis Page 31: Page 32: Page 33: Rails Refactorings Page 34: Example Move Data From View Into Presenter Page 35: What is a Presenter? An object responsible for view-related logic and behavior. Page 36: Presenters are decorators, they wrap objects, and delegate Page 37: Presenters can work for individual resources / models ie: PersonPresenter Page 38: Presenters can work for specific UI components ie: ProjectWidgetPresenter Page 39: Example Move Data From View Into Presenter Page 40: Example Move View Logic From View Into Presenter Page 41: Example Move Model Logic Into Model Page 42: Example Extract Operations Into Service Page 43: What is a Service? An operation that stands alone with no encapsulated state. Page 44: class ProjectService def create_project generate new project logo automatically create the project send out email notifications ... end end Page 45: class AccountService def transfer_funds(source, target, amount) transaction do source.withdraw(amount) target.deposit(amount) end end end Page 46: Example Extract Operations Into Service Page 47: Example Introduce Result Object Page 48: Example Organize Large Model w/Mixins Page 49: Example Extract RJS From Inline Update Page 50: Example Extract RJS Into Renderer Page 51: Example Replace Instance Variable w/Local Variable In Partial Page 52: Example Extract Class from Long Method Page 53: More Rails Refactorings - Extract Complex Creation Into Factory - Move Before Filter and Friends Into App. Service - Move View Data From Controller Into Presenter - Move View Logic From Controller Into Presenter - Move Extrinsic Callback Into Observer - Move View Logic From Model Into Presenter Page 54: Questions? Page 55: References / Resources Books - Refactoring: Improving The Design Of Existing Code, Martin Fowler - The Pragmatic Programmer, Dave Thomas and Andy Hunt - Domain Driven Design: Tackling The Heart Of Complexity In Software, Eric Evans Online Resources - http://www.refactoring.com Page 56: References / Resources Example Application based on Strac - Example Agile Project Management, Zach Dennis and Drew Colthorp http://github.com/zdennis/strac/tree/refactoring Strac - Open Source Agile Project Management, Mark VanHolstyn and Zach Dennis http://github.com/mvanholstyn/strac/tree/master Page 57: Thanks for attending! Page 58: