Dependency Injection

Transcript

1. Dependency Injection
   An overview
   Jason Ragsdale – DPUG 4/13/2010
   

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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)
   

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3. Our Interface
   

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4. Highly coupled dependency
   

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5. Manually-injected dependency
   

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6. Framework-managed dependency
   injection
   

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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
   

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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.
   

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9. References
   ● http://en.wikipedia.org/wiki/Dependency_injection
   ● http://martinfowler.com/articles/injection.html
   

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