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Dealing with dependencies

Dealing with dependencies. jon fuller. IoC , DI, DIP, OMG, WTF?. Acronym overload! Whats it all mean? IoC – Inversion of Control DI – Dependency Injection DIP – Dependency Inversion Principle Often used interchangeably, but we’ll see they aren’t really all the same thing. IoC.

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Dealing with dependencies

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  1. Dealing with dependencies jon fuller

  2. IoC, DI, DIP, OMG, WTF? Acronym overload! Whats it all mean? • IoC – Inversion of Control • DI – Dependency Injection • DIP – Dependency Inversion Principle Often used interchangeably, but we’ll see they aren’t really all the same thing.

  3. IoC • Declarative – Separation of what to do and how to do it • Hollywood Principle • Examples: • Winforms/WPF • Ruby On Rails • Dependency Injection

  4. DI[P] • Uncle Bob Says High-level modules should not depend on low-level modules. Both should depend on abstractions. • Dependencies are supplied by the caller of a module • The D in SOLID (saved the best for last? nah.)Single Responsibility PrincipleOpen Closed PrincipleLiskov Substitution PrincipleInterface Segregation PrincipleDependency Inversion Principle source

  5. But Why? • It’s Awesome! • All the cool kids are doing it! (read: Fowler, Uncle Bob, Me (did you know Cool is my middle name?), etc.) • Simplicity • Testability* • Configurability source * Loaded Term… Watch out!

  6. Example – Non-DI Tightly coupled!

  7. Example – DI Injected Dependency Injection site

  8. Yeah, but… You: Someone has to create that dependency right? Me: Yep You: Ah, so we just push it up one level. Wait, where’s the benefit in that? Me: Enter Container. source

  9. Example – DI w/Container Configure Container Get instance from container

  10. Example – DI w/Container (Autowire) Register the finder Configure finder Autowire, Automagic

  11. Conventions/Features • Constructor Injection • Property Injection • Lifecycle Management • AOP/Interception

  12. Common Implementations • .NET • Windsor • StructureMap • Unity • Ninject • AutoFac • Spring.NET • Java • Spring • Nano/Pico Container • Tapestry/Hivemind • Ruby • Copland

  13. Configuration Management • Fluent (StructureMap) • DSL (Binsor) • XML(Windsor)

  14. Testability • Loosely Coupled/Highly Cohesive • TDD • Mocking

  15. Resources • Fowler • http://martinfowler.com/articles/injection.html • http://martinfowler.com/bliki/InversionOfControl.html • Uncle Bob • www.objectmentor.com/resources/articles/dip.pdf • StructureMap – http://structuremap.sourceforge.net/ • Windsor – http://www.castleproject.org • Unity – http://www.codeplex.com/unity • Common Service Locator – http://www.codeplex.com/CommonServiceLocator

  16. Questions?/Comments/Feedback source

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