[ CHALLENGE ]: dependency injection

Question

Show an implementation of dependency injection in your favourite language AND describe in what situation you would use dependency injection.

Answer 1

Here is an example of dependency injection in different languages. If you run it, you will get this text:
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Demo that shows usage of dependency injection
Dependency injection is used for hardware abstraction, which has the following advantages:
- I can simply use a simulator if I don't have hardware
- if the hardware ever changes, I only need to implement a new implementation of the interface to support the new hardware, the rest of the system stays the same!
- I can use mocks to unit test my class without having an implementation at all!

Demo: calling DoIt that switches the light on and off:

LightSimulator: switched light ON
LightSimulator: switched light OFF
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Any code that depends on other code can benefit from dependency injection: you get a clear separation between what you need and *how* it's implemented. This makes your code easier to (unit) test and more resilient to changes.

C#:
https://code.sololearn.com/cY9XoZEnG3M5/#cs

Java:
https://code.sololearn.com/cwtUzejrEncH/#java

C++:
https://code.sololearn.com/ckfFj1tn00SG/#cpp

C:
https://code.sololearn.com/cgFqvBW20pPj/#c

Python:
https://code.sololearn.com/c0F2op5hX8E0/#py