Parallel Keynote: 8 Lines of Code
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Video and slides synchronized, mp3 and slide download available at URL http://bit.ly/14ExI0I. Greg Young discusses eight lines of very common code finding in them massive numbers of dependencies and difficulties, looking for ways to get rid of them. Filmed at qconlondon.com. Greg Young is an independent consultant and entrepreneur. He is always involved with many concurrent projects, currently these include building out a distributed event store and mighty moose (a continuous test runner). For periods of years Greg has been known to stop living anywhere and just travel. Twitter: @gregyoung
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Parallel Keynote: 8 Lines of Code
- 1. 8 Lines of Code Greg Young
- 2. InfoQ.com: News & Community Site • 750,000 unique visitors/month • Published in 4 languages (English, Chinese, Japanese and Brazilian Portuguese) • Post content from our QCon conferences • News 15-20 / week • Articles 3-4 / week • Presentations (videos) 12-15 / week • Interviews 2-3 / week • Books 1 / month Watch the video with slide synchronization on InfoQ.com! http://www.infoq.com/presentations /8-lines-code-refactoring
- 3. Presented at QCon London www.qconlondon.com Purpose of QCon - to empower software development by facilitating the spread of knowledge and innovation Strategy - practitioner-driven conference designed for YOU: influencers of change and innovation in your teams - speakers and topics driving the evolution and innovation - connecting and catalyzing the influencers and innovators Highlights - attended by more than 12,000 delegates since 2007 - held in 9 cities worldwide
- 4. Simplicity
- 5. I am stupid to work otherwise. Fancy code befuddles me.
- 6. public class DeactivateInventoryItem { private readonly ItemRepository repository; public DeactivateInventoryItem(ItemRepository repository) { this.repository = repository; } public void Deactivate(Guid id, string reason) { var item = repository.GetById(id); item.Deactivate(reason); repository.Save(item); } }
- 7. [Transactional] [RequiresPermission(“admin”)] [Logged] [EatsExceptions] [DoesBadThingsWhenYouArentWatching] public class DeactivateInventoryItem { private readonly ItemRepository repository; public DeactivateInventoryItem(ItemRepository repository) { this.repository = repository; } public void Deactivate(Guid id, string reason) { var item = repository.GetById(id); item.Deactivate(reason); } }
- 8. Simplicity?
- 9. <bean id="moreComplexObject" class="example.ComplexObject"> <!-‐-‐ results in a setAdminEmails(java.uNl.ProperNes) call -‐-‐> <property name="adminEmails"> <props> <prop key="administrator">administrator@example.org</prop> <prop key="support">support@example.org</prop> <prop key="development">development@example.org</prop> </props> </property> <!-‐-‐ results in a setSomeList(java.uNl.List) call -‐-‐> <property name="someList"> <list> <value>a list element followed by a reference</value> <ref bean="myDataSource" /> </list> </property> <!-‐-‐ results in a setSomeMap(java.uNl.Map) call -‐-‐> <property name="someMap"> <map> <entry key="an entry" value="just some string"/> <entry key ="a ref" value-‐ref="myDataSource"/> </map>
- 10. [Transactional] [RequiresPermission(“admin”)] [Logged] [EatsExceptions] [DoesBadThingsWhenYouArentWatching] public class DeactivateInventoryItem { private readonly ItemRepository repository; public DeactivateInventoryItem(ItemRepository repository) { this.repository = repository; } public void Deactivate(Guid id, string reason) { var item = repository.GetById(id); item.Deactivate(reason); } }
- 11. [Transactional] [RequiresPermission(“admin”)] [Logged] [EatsExceptions] [DoesBadThingsWhenYouArentWatching] public class DeactivateInventoryItem { private readonly ItemRepository repository; public DeactivateInventoryItem(ItemRepository repository) { this.repository = repository; } public virtual void Deactivate(Guid id, string reason) { var item = repository.GetById(id); item.Deactivate(reason); } }
- 12. public object Foo() { return this; }
- 14. If you find you need an extension to your ide to understand what’s going on. Its probably not simple.
- 15. What’s the root of the problem?
- 16. public void Deactivate(Guid id, string reason) { var item = repository.GetById(id); item.Deactivate(); } public void Reactivate(Guid id, DateTime effective, string reason) { var item = repository.GetById(id); item.Deactivate(); } public void CheckIn(Guid id, int count) { var item = repository.GetById(id); item.Deactivate(); }
- 19. public void Handle(DeactivateCommand c) { var item = repository.GetById(c.id); item.Deactivate(); } public void Handle(ReactivateCommand c) { var item = repository.GetById(c.id); item.Reactivate(); } public void Handle(CheckInCommand c) { var item = repository.GetById(c.id); item.CheckIn(c.quantity); }
- 20. interface Handles<T> where T:Command { void Handle(T command); }
- 21. class LoggingHandler<T> : Handles<T> where T:Command { private readonly Handles<T> next; public LoggingHandler(Handles<T> next) { this.next = next; } public void Handle(T command) { myLoggingFramework.Log(command); next.Handle(command); } } var handler = new LoggingHandler<DeactivateCommand>( new DeactivateCommandHandler(...) );
- 23. public class DeactivateInventoryItem :Handles<DeactivateCommand> { private readonly ItemRepository repository; public DeactivateInventoryItem(ItemRepository repository) { this.repository = repository; } public void Handle(DeactivateCommand command) { var item = repository.GetById(command.id); item.Deactivate(cmd.Reason); } }
- 24. public class DeactivateInventoryItem :Handles<DeactivateCommand> { private readonly ItemRepository repository; public DeactivateInventoryItem(ItemRepository repository) { this.repository = repository; } public void Handle(DeactivateCommand command) { var item = repository.GetById(command.id); item.Deactivate(cmd.Reason); } }
- 25. class Handlers { public static void Handle(ItemRepository repository, DeactivateCommand c) { var item = repository.GetById(c.id); item.Deactivate(); } public static void Handle(ItemRepository repository, ReactivateCommand c) { var item = repository.GetById(c.id); item.Deactivate(); } public static void Handle(ItemRepository repository, CheckInCommand c) { var item = repository.GetById(c.id); item.Deactivate(); }
- 26. Back to the same problem!
- 27. public static int Add(int a, int b) { return a + b; }
- 28. public static int Add(int a, int b) { return a + b; } var add5 = x => Add(5, x);
- 29. public static void Deactivate(ItemRepository repository, DeactivateCommand c) { var item = repository.GetById(c.id); item.Deactivate(); }
- 30. public static void Deactivate(ItemRepository repository, DeactivateCommand c) { var item = repository.GetById(c.id); item.Deactivate(); } var nodepends = x => Deactivate(new ItemRepository(), x);
- 31. void BootStrap() { handlers.Add(x => Deactivate(new ItemRepository(), x)); handlers.Add(x => Reactivate(new ItemRepository(), x)); handlers.Add(x => CheckIn(new ItemRepository(), new BarService(), x)); }
- 32. void BootStrap() { handlers.Add(x => Deactivate(() => new ItemRepository(), x)); handlers.Add(x => Reactivate(() => new ItemRepository(), x)); handlers.Add(x => CheckIn(() => new ItemRepository(), new BarService(), x)); }
- 33. public static void Log<T>(T command, Action<T> next) where T:Command { myLoggingFramework.Log(command); next(command); }
- 34. class LoggingHandler<T> : Handles<T> where T:Command { private readonly Handles<T> next; public LoggingHandler(Handles<T> next) { this.next = next; } public void Handle(T command) { myLoggingFramework.Log(command); next.Handle(command); } } var handler = new LoggingHandler<DeactivateCommand>( new DeactivateCommandHandler(...) );
- 35. <bean id="moreComplexObject" class="example.ComplexObject"> <!-‐-‐ results in a setAdminEmails(java.uNl.ProperNes) call -‐-‐> <property name="adminEmails"> <props> <prop key="administrator">administrator@example.org</prop> <prop key="support">support@example.org</prop> <prop key="development">development@example.org</prop> </props> </property> <!-‐-‐ results in a setSomeList(java.uNl.List) call -‐-‐> <property name="someList"> <list> <value>a list element followed by a reference</value> <ref bean="myDataSource" /> </list> </property> <!-‐-‐ results in a setSomeMap(java.uNl.Map) call -‐-‐> <property name="someMap"> <map> <entry key="an entry" value="just some string"/> <entry key ="a ref" value-‐ref="myDataSource"/> </map>
- 36. public static void Log<T>(T command, Action<T> next) where T:Command { myLoggingFramework.Log(command); next(command); }
- 37. Understand the problem a tool or idea solves well
- 38. If you need to add stuff to your IDE you are probably on the wrong path.
- 39. You own all code in your project. Your boss doesn’t care if the bug happened in someone else’s library!