Object Oriented Design Principles
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The document serves as a guide to well-designed application development using Laravel and emphasizes the importance of object-oriented design principles, specifically the SOLID principles. It outlines various design principles, compares design patterns, and offers practical advice for building maintainable and testable applications. Key concepts include the separation of concerns, interfaces, and recognizing symptoms of bad design to avoid common pitfalls in software development.
Object Oriented Design Principles
- 1. >< nextprevious Object Oriented Design Principles How to become a SOLID programmer Tran Duc Thang Framgia Vietnam - Business Strategy Office - Human Development Section A guide to make a well-designed application with Laravel 1
- 2. >< nextprevious “Proper Object Oriented design makes a developer's life easy, whereas bad design makes it a disaster.” 2
- 3. Table of Contents 01 Design Principles first look ‣ What is Design Principle? ‣ Design Principle vs Design Pattern 02 03 04 >< nextprevious SOLID in depth ‣ What are SOLID? ‣ Decoding SOLID ‣ Other related principles Building well-design app ‣ A story with MVC ‣ Some ideas when working with Laravel ‣ Symptoms of Bad Design Summarisation ‣ Annotations, disclaims and notes 3
- 4. >< nextprevious Design Principles • Object Oriented Design Patterns ‣ A general repeatable solution to a commonly occurring problem in software design. ‣ A description or template for how to solve a problem that can be used in many different situations. ‣ Gained popularity after the book “Design Patterns: Elements of Reusable Object- Oriented Software” was published in 1994 by the so-called “Gang of Four” 4
- 5. >< nextprevious Design Principles • Object Oriented Design Principles ‣ Associated to Robert Cecil Martin who gathered them in “Agile Software Development: Principles, Patterns, and Practices” ‣ Represent a set of guidelines that ensures OOP concepts, then helps us to avoid having a bad design. ‣ It’s abstract. (Not concrete). 5
- 6. >< nextprevious Design Principles • Robert Cecil Martin ‣ Agile software development: principles, patterns, and practices. ‣ Clean code: a handbook of agile software craftsmanship. ‣ The clean coder: a code of conduct for professional programmers. 6
- 7. >< nextprevious Design Principles • Some Software Design Principles in examples ‣ DRY (Don’t Repeat Yourself) ‣ KISS (Keep It Simple, Stupid!) ‣ YAGNI (You Aren't Gonna Need It) 7
- 8. >< nextprevious Design Principles • Design Patterns vs Design Principles ‣ Principles: low-level, general guidelines ‣ Patterns: high-level, concrete examples. Provide reusable solutions to real world problems. ‣ Good Design Patterns should comply good Design Principles 8
- 9. >< nextprevious SOLID in depth • What are SOLID? ‣ A mnemonic acronym introduced by Michael Feathers for the “first five principles” named by Robert Cecil Martin. ‣ Single responsibility principle ‣ Open/closed principle ‣ Liskov substitution principle ‣ Interface segregation principle ‣ Dependency inversion principle 9
- 10. >< nextprevious SOLID in depth • Single responsibility principle (SRP) ‣ A class should have only a single responsibility. In other words, a class should have one, and only one, reason to change. 10
- 11. >< nextprevious SOLID in depth 11
- 12. >< nextprevious SOLID in depth • Open/closed principle (OCP) ‣ Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification ‣ An entity can allow its behaviour to be extended without modifying its source code 12
- 13. >< nextprevious SOLID in depth 13
- 14. >< nextprevious SOLID in depth • Liskov substitution principle (LSP) ‣ If S is a subtype of T, then objects of type T may be replaced with objects of type S without altering any of the desirable properties of that program. 14
- 15. >< nextprevious SOLID in depth 15
- 16. >< nextprevious SOLID in depth • Interface segregation principle (ISP) ‣ No client should be forced to depend on methods it does not use. ‣ Many client-specific interfaces are better than one general-purpose interface. 16
- 17. >< nextprevious SOLID in depth 17
- 18. >< nextprevious SOLID in depth • Dependency inversion principle (ISP) ‣ High-level modules should not depend on low-level modules. Both should depend on abstractions. ‣ Abstractions should not depend on details. Details should depend on abstractions. 18
- 19. >< nextprevious SOLID in depth 19
- 20. >< nextprevious SOLID in depth Some other concepts related to SOLID • Separation of Concerns (SoC) ‣ The process of breaking a computer program into distinct features that overlap in functionality as little as possible 20
- 21. >< nextprevious SOLID in depth • Law of Demeter (LoD) aka Principle of Least Knowledge ‣ Each unit should have only limited knowledge about other units: only units "closely" related to the current unit. ‣ Each unit should only talk to its friends; don't talk to strangers. ‣ Only talk to your immediate friends. 21
- 22. >< nextprevious SOLID in depth • Program to an interface, not an implementation ‣ One of good object-oriented design techniques that GoF mentioned in “Design Patterns: Elements of Reusable Object- Oriented Software” 22
- 23. >< nextprevious SOLID in depth • SOLID in Action - Checkout examples at Github https://github.com/wataridori/solid-php-example 23
- 24. >< nextprevious SOLID in depth All SOLID principles work perfectly together. Breaking one principle may also make some (or even all) of the remaining principles become broken too! 24
- 25. >< nextprevious Building well-designed app • The MVC Story: Model vs Controller ‣ Where to put your business logic? ‣ Fat Controllers - Skinny Models? ‣ Fat Models - Skinny Controllers? ‣ Fat Models - Fat Controllers? 25
- 26. >< nextprevious “MVC is killing you” ~ Taylor Otwell - Laravel’s creator ~ 26
- 27. >< nextprevious Think different! “Think outside of the ‘Model’ Box” 27
- 28. >< nextprevious • Some ideas when working with Laravel ‣ Get rid of “Model” with lots of business, try “Entity” ‣ Repository design pattern for Data Access Layer ‣ Form Request Validation ‣ Job ‣ Event ‣ View Presenter, or any kind of wrappers that helps you get rid of God Object ‣ Design Patterns ‣ … Building well-designed app 28
- 29. >< nextprevious • Symptoms of Bad Design ‣ Rigidity ‣ Fragility ‣ Immobility ‣ Viscosity ‣ Needless Complexity ‣ Needless Repetition ‣ Opacity Building well-designed app 29
- 30. >< nextprevious • Funny: Avoid STUPID codes ‣ Singleton Pattern ‣ Tight coupling ‣ Untestability ‣ Premature Optimization ‣ Indescriptive Naming ‣ Duplication Building well-designed app 30
- 31. >< nextprevious Summarisation • SOLID principles, as well as other design principles and design patterns help you to build large applications which are easy-to-be- extended, easy-to-be-maintained, easy-to-be- tested. 31
- 32. >< nextprevious Summarisation • SOLID principles, as well as other design principles and design patterns help you to build LARGE applications which are easy-to-be- extended, easy-to-be-maintained, easy-to-be- tested. • Principles are just a set of GUIDELINES. They are not LAWS! • Don’t take the above argument as a reason to be lazy! 32
- 33. >< nextprevious Summarisation Extract Responsibilities && Programming to the Interface 33
- 34. >< nextprevious References ‣ https://en.wikipedia.org/wiki/SOLID_(object-oriented_design) ‣ http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod ‣ http://www.oodesign.com/ ‣ https://lostechies.com/derickbailey/2009/02/11/solid- development-principles-in-motivational-pictures/ ‣ https://nikic.github.io/2011/12/27/Dont-be-STUPID-GRASP- SOLID.html ‣ http://williamdurand.fr/2013/07/30/from-stupid-to-solid-code/ ‣ http://www.codeproject.com/Articles/567768/Object-Oriented- Design-Principles ‣ “Design Principles and Design Patterns” - Robert C. Martin ‣ “From Apprentice To Artisan” - Taylor Otwell 34
- 35. >< nextprevious Thank you for listening! Q&A For any discussion, you can refer this post on Viblo https://viblo.asia/thangtd90/posts/pVYRPJPmG4ng 35