# Programming Principles In A Nutshell

Keep in mind

• they are not tied to a specific language or technology
• don’t memorize them
• use wisely, they don’t fit everywhere
• they are very universal (single function, whole architecture, database/API, drivers/interfaces)
• “interface” could mean like from Java language or from the printer’s driver (doesn’t matter)

SOLID

• S - SRP - Single Responsibility Principle

  one responsibility

• O - OCP - Open-closed Principle

  expandable without modification

• L - LSP - Liskov Substitution Principle

  while extending, keep or extend the interface

• I - ISP - Interface segregation Principle

  dedicated are better than generic

• D - DIP - Dependency inversion Principle

  high-level things can’t depend on those at low-level

LC & HC

• Loose coupling

  unrelated elements should have as few dependencies as possible

• High cohesion

  related elements should be close to each other

DI & IoC

• Depencendy Injection

  accept instances of others rather than creating them within

• Inversion Of Control

  do not create dependencies, accept them (DI); delegation of events instead of sequences

Last but not least

• DRY - Don’t Repeat Yourself

  divide and conquer - refactor

• KISS - Keep It Simple Stupid

  don’t overengineer - use basics

• YAGNI - You Aren’t Gonna Need It

  requirements are always changing