IoC, AOP and more

Question

What is an IoC container?

What is an IoC/DI framework?

Why do we need a framework for IoC/DI?

Is there any relationship between IoC/DI and AOP?

Answer 1

From a semantics point of view...

Dependency Injection itself implies a dependency, i.e. something that is required for construction/use (the application's "core concerns"). For example, a car is not a car without an engine.

Aspects are described as being cross-cutting to the application's core concerns. That means both separate from and non-crucial to the core concerns (you could think of them as "nice-to-haves"). Since the application can run without aspects, are they really dependencies? For example, a car is still a car even without an immobiliser.

(Of course, this is from a theoretical standpoint. In the real world matters like security are often as crucial to the existence of a marketable product as the core concerns themselves.)

So in while in practice DI can be used to implement aspects, I would not call that process true DI. This is coming from someone who uses constructor injection exclusively.