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Do you inject your dependencies?
  v2.0 Posted at 2/11/2012 6:11 PM by Adam Stephensen

Injecting your dependency gives you:

  • Loosely coupled classes
  • Increased code reusing
  • Maintainable code
  • Testable methods
  • All dependencies are specified in one place
  • Class dependencies are clearly visible in the constructor
inject Figure: Bad Example – A solution where each layer depends on static classes is not maintainable or testable inject Figure: Good Example – Dependencies in each layer should only be interfaces. This allows dependencies to be easily interchanged and unit tests to be written against mock/fake objects inject Figure: Bad Example – Classes should not include dependencies on database classes or business objects. Both of these classes may contain dependencies on external services like web services or databases inject Figure: Good Example – The dependencies are injected into the class. This enables alternative classes to be injected. For example, a DHLShippingCalculator should be easily substituted for a FedexShippingCalculator. A MockShippingCalculator and MockProductRepository could be injected if we wanted to run unit tests
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