SOLID principles

Single Responsibility

Open/Close

Liskov's Substitution

Interface Segregation/ Inversion of Control / Isolation

Dependency Inversion / Dependency injection/ Durability

1. Single responsibility:

⁃	any class/function/module (unit-of-code) should have a single, well-defined respobsility
⁃	any piece of code should have only 1 reason to change
⁃	if you identify that a piece of code has multiple responsibilities - split the code into multiple units

2. Open/Close:

⁃	Code should be closed for modification, yet, it should remain open for extension!
⁃	modification: changing existing code
⁃	you might have to change it for bug fixes
⁃	but you should not change existing code for changing requirements
⁃	extension: adding new functionality in the face of changing requirements

3. Liskovs Substitution Principle:

  - Child classes should not violate expectations set by the parent class
  - Any object of 'class Parent' must be replacable (without issues) by a object of class Child extends Parent
  - Child classes should not be forced to implement behavior that they can't exhibit (don't force all Birds to fly, because some of them can't)

4. Interface Segregation Principle:

  - Keep your interfaces minimal
  - clients of your interfaces should not be forced to implement behavior that they don't need

5. Dependcy Inversion Principle:

   - Code should NEVER depend on Low level implementation details
  - Code should dependend ONLY on high level abstractions
Dependency Injection:

Don't create the dependencies yourself - let your clients supply (inject) dependencies into you (via constructor/function params)