I already talked about the subject of Dependency Inversion here and of course the way to implement Dependency Inversion is to use Dependency Injection.
First let’s go back to what is Dependency Injection. Dependency injection is used to inject real implementations into a class that uses abstract interfaces instead. So let’s say a Presenter Class uses of View Class. If you are using SOLID, then your Presenter Class will “see” the View Class thru an abstract interface (a contract) and thus the dependency to the View Class will be reversed as you can see in the Fig-1.
When this is done, you can “insert” whatever View in the Presenter as long as it respects the View Protocol contract.
To do the insertion, you will use Dependency Injection. There are 2 types of Dependency Injection :
- Dependency Injection at instanciation
- Dependency Injection by modification