Dependency Injection - Advanced Coding

Dependency Injection (DI) is a design pattern in which an object receives other objects that it depends on.
A class doesn't know where it's dependencies came from and doesn't even need to pass dependencies to any child objects it creates.

⭐️ There are four roles an object may play in Dependency Injection.
📌 Service - The dependency or object to be used.
📌 Client - The object that is using and depending on the service.
📌 Interface - Defines how the client can use the service.
📌 Injector - The object responsible for constructing the services and injecting them into the client.

⭐️ If you're confused, no worries, here are examples of all the roles
📌 Service - Class Retriever, implements the IDog interface.
📌 Client - Class Walk, requires an IDog object.
📌 Interface - IDog, defines the methods for all Dogs.
📌 Injector - MyInjector, creates the correct type of dog and injects it.

⭐️ The power behind this design pattern is the loose coupling architecture.
💻 We could easily create a new type of dog, Pug, inject it, and the Walk class will work fine.
💻 Passing dependencies as arguments are no longer required.
💻 All dependency logic is offloaded into Injectors, allowing Dog to focus on being a dog.
💻 DI allows for factories to be injected also.

➡️ There is sometimes a performance cost depending on the implementation.
➡️ DI assets exist for Unity, we'll be covering this soon.

---