Mastering "D" in S.O.L.I.D

“High-level modules should not depend on low-level modules”

Don’t tightly couple your main code with details.
Both should depend on abstractions (like interfaces or abstract classes).“

Daily Life Example

Imagine:

• High-level module = TV Remote

• Low-level module = TV

Without Dependency Inversion:

Remote directly knows about SamsungTV and its buttons

• This means the Remote will only work with a Samsung TV.

• If you bring an LG TV, you’ll need to change the Remote code.

• This is tight coupling and bad design.

With Dependency Inversion:

• We create a TV interface that defines basic functions:

interface TV {
    void turnOn();
    void turnOff();
    void changeChannel(int ch);
}

• Now, SamsungTV and LGTV both implement this interface.

• Remote depends on the TV interface, not a specific TV.

class Remote {
    TV tv;  // depends on abstraction
    void pressPower() { tv.turnOn(); }
}

• Now the Remote can work with any TV.

• If you change the TV, Remote code does not need to change. ✅

Summary

• DIP means: "High-level code should not depend on low-level code. Work via abstractions."

• Real-life example: Remote depends on TV interface, not Samsung or LG TV.

• Benefit: Flexible, maintainable, easy to extend in the future.