What is depedency inversion principle?

Question

The principle states : "High-level modules should not depend on low-level modules. Both should depend on abstractions."
Can you make it clear by some example?

Answer 1

Inversion of Control and Dependency Injection are two concepts used in unit testing.

When we unit test, we do not want the app to go to a database or call a service. So, if our high level module depends on using a low level module, then we can't unit test it.

If our high level module depends on an interface, we can inject a mock/fake/stub for testing.

Hopefully this code will help. Let me know if you need more information.

https://code.sololearn.com/c16dDk3NKWtw/?ref=app