Dependency Injection

Transcript

1. Dependency Injection An overview Jason Ragsdale – DPUG 4/13/2010
2. Basics • DI is a technique for supplying an external dependency to a software component • DI involves at least three elements • A dependent • Dependencies • An injector (provider / container)
3. Our Interface
4. Highly coupled dependency
5. Manually-injected dependency
6. Framework-managed dependency injection
7. Benefits and Drawbacks • Reduction of boiler-plate code • Flexibility in changing out external dependencies • Testing in general, ability to inject mock or dev dependencies
8. Types of DI • Interface Injection • in which the exported module provides an interface that its users must implement in order to get the dependencies at runtime. • Setter Injection • in which the dependent module exposes a setter method that the framework uses to inject the dependency. • Constructor Injection • in which the dependencies are provided through the class constructor.
9. References • http://en.wikipedia.org/wiki/Dependency_injection • http://martinfowler.com/articles/injection.html