Actual software projects will usually combine multiple components that will have to be used together. Most of the time, these components will depend on others, which in turn depend on other components and so on. This makes creating objects in an application hard because we also need to create the objects they depend on and so on. This is where dependency injection comes in handy.
So what exactly is dependency injection? It turns out to be something really simple—every single class that has an object as a parameter in their constructor actually is an example of a dependency injection. The reason is that the dependency is injected into the class rather than instantiated inside it. Developers should actually try to use this kind of approach instead of creating objects inside a constructor. There are many reasons for this, but one of the most important ones is the fact that components can become tightly coupled and practically untestable.
Dependency...