SOLID - Principles

Make your codebase great again

S ingle Responsibility

O pen-Closed

L iskov-Substitution

​I nterface-Segregation

D ependency-Inversion

S ingle Responsibility

  • Defined by Robert C. Martin (Uncle Bob) in his book "Agile Software Development, Principles, Patterns and Practices" in 2002

 

Definition:

A class should have only one reason to change.

 

O pen-Closed

  • Introduced by Bertrand Meyer (french programmer) in his book 'Object-Oriented Software Construction' in 1988

 

Definition:

Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification.

 

 

  • First introduced by Barbara Liskov in a 1987 conference keynote
  • Then published by Barbara Liskov and Jeanette Wing in 1994

Definition:

Let q(x) be a property provable about objects x of type T. Then q(y) should be provable for objects y of type S where S is a subtype of T

 

in simple terms:

Child classes should never break the parent class' type definitions.

L iskov-Substitution

  • First introduced by Robert C. Martin during a consulting-Job for Xerox
  • Problem was, that in a printer-software every Job depended on one Single Class
  • Every slight Change resulted in an extensive build-process (> 1hr)
  • Solution was to segregate functionality and incapsulate them within separated Interfaces/classes

​I nterface-Segregation

  • Defined by Robert C. Martin in his book  'Agile Software Development, Principles, Patterns, and Practices'
  • Always depend on abstract interfaces instead of implementations
  • Classes can use interfaces or implement interfaces
  • Allows decoupling, so consumer can handle every implementation of the interface

D ependency-Inversion

Thanks for your time and happy Coding!

Programming - Challange

Implement a Score-System for a turned-based game (like Poker) (The game(s) can be stubbed)

  • it should:
    • be able to keep track of scores for each user
    • handle a variable amount of players
    • offer an interface to games with at least:
      • addScore
      • getScore
      • reduceScore
      • getResults
    • get a Winner for different games (easy rules like highest score wins lowest score wins)
    • get a List of all Players and their scores
    • keep track of a series of games
    • export results as csv

SOLID - Principles

By sd_alt

SOLID - Principles

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