Dependency Injection

Dependency Injection


Jason Ragsdale

April 13, 2010


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    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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    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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    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.