week 5 summary

Gergő Pintér, PhD

gergo.pinter@uni-corvinus.hu

software design and architecture stack

based on Khalil Stemmel’s figure [1]

gang of four (GoF) design patterns

  • GoF: Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides
  • 23 common software design patterns
    • published in “Design Patterns: Elements of Reusable Object-Oriented Software” (1994) [2]
  • provides solutions to common design problems
  • categorized into three main groups
    1. creational
    2. structural
    3. behavioral

read about the design patterns in details, for example at refactoring.guru

GoF design patterns in functional programming

OO pattern FP pattern
factory pattern function
strategy pattern function
decorator pattern function
visitor pattern function
… …

Peter Norvig demonstrated that 16 out of the 23 patterns are simplified or eliminated by language features in Lisp or Dylan (1998) [3]

more about it from Scott Wlaschin [4]

SOLID principles

SOLID is a mnemonic acronym for five design principles intended to make object-oriented designs more understandable, flexible, and maintainable [5]

single responsibility principle
a class should do one thing and therefore it should have only a single reason to change
open-closed principle
classes should be open for extension and closed to modification
Liskov substitution principle
if class A is a subtype of class B, B should be able to replaced with A without disrupting the behavior of the program
interface segregation principle
many client-specific interfaces are better than one general-purpose interface. Clients should not be forced to implement a function they do no need.
dependency inversion principle
modules should depend upon interfaces or abstract classes, not concrete classes. It’s an inversion because implementations depend upon abstractions and not the other way round

based on [6], [7]

coupling

  • the degree of interdependence between software modules
  • coupling is usually contrasted with cohesion
    • low coupling often correlates with high cohesion, and vice versa
from Wikimedia | public domain

source Wikipedia [8]

architectural styles / topologies

architectural patterns

MVC

ASP.NET, Django (Python), Ruby on Rails, Laravel (PHP)

MVP

Windows Forms, Java Swing

MVVM

WPF, AngularJS

  • view is responsible for rendering UI
  • controller responds to the user input (in MVC) and performs interactions on the data model
  • model is responsible for managing the data

references

[1]
K. Stemmler, “How to learn software design and architecture.” https://khalilstemmler.com/articles/software-design-architecture/full-stack-software-design , 28-Sep-2019.
[2]
E. Gamma, R. Helm, R. Johnson, and J. Vlissides, Design patterns: Elements of reusable object-oriented software. Pearson Education, 1994.
[3]
P. Norvig, “Design patterns in dynamic languages.” http://www.norvig.com/design-patterns/ , 17-Mar-1998.
[4]
S. Wlaschin, “Functional programming design patterns.” https://fsharpforfunandprofit.com/fppatterns/ , Dec-2014.
[5]
Wikipedia contributors, “SOLID — Wikipedia, the free encyclopedia.” https://en.wikipedia.org/w/index.php?title=SOLID&oldid=1237710587, 2024.
[6]
S. Millington, “A solid guide to SOLID principles.” https://www.baeldung.com/solid-principles , 05-Feb-2019.
[7]
S. Oloruntoba and A. S. Walia, “SOLID: The first 5 principles of object oriented design.” https://www.digitalocean.com/community/conceptual-articles/s-o-l-i-d-the-first-five-principles-of-object-oriented-design , 23-Apr-2024.
[8]
Wikipedia contributors, “Coupling (computer programming) — Wikipedia, the free encyclopedia.” https://en.wikipedia.org/w/index.php?title=Coupling_(computer_programming)&oldid=1245630908, 2024.