Common design patterns in php
- 1. Common PHP Design Patterns David Stockton Front Range PHP User Group - Feb 18, 2015
- 2. What are design patterns?
- 4. Gang of Four Cartman, Kyle, Stan, Kenny
- 5. Gang of Four Gamma, Helm, Johnson, Vlissides
- 6. What arenât design patterns?
- 9. Scratch is Legos for Coding This talk is not about scratch
- 10. Design Patterns Help You Talk to Other Coders
- 11. Hey, Iâm building a chunk of code that is used to build an object which has a lot of dependencies and setup and each of those has a few of their own so this piece of code will take care of putting together all those pieces so that when I need the object I just have to ask this one object to give me the other one and then I can use it where ever I need instead of having to build a huge dependency tree before using this codeâŠ
- 12. LOL WUT?
- 13. Iâm building a factory.
- 14. What does a factory do? âą Builds objects âą Encapsulates building of objects so thereâs only one place to ïŹnd how to build it
- 16. Singleton
- 17. Singleton There can be only one
- 18. Singleton âą For classes where we want only one instance
- 20. Downsides of Singleton âą It is a global âą Hard to test âą Better ways to do this
- 21. Another pattern description âą Iâm going to create a shopping cart where I can choose how the discounts or promo codes will be applied by injecting various objects, each of which can include how to apply these discounts; for example apply discounts only to items that donât have other discounts, apply discount percentage on the base price not counting already applied discounts, apply discount percentage after other applied discounts, apply a ïŹat amount of a discount for each item, apply a discount on an item based on what type of item it is, etc
- 22. Strategy pattern âą Iâm going to create a shopping cart where I can choose how the discounts or promo codes will be applied by injecting various objects, each of which can include how to apply these discounts; for example apply discounts only to items that donât have other discounts, apply discount percentage on the base price not counting already applied discounts, apply discount percentage after other applied discounts, apply a ïŹat amount of a discount for each item, apply a discount on an item based on what type of item it is, etc
- 23. Strategy pattern âą Allow injection of object that provides some aspect of the functionality âą Algorithmâs functionality can be decided at run-time âą Examples: âą usort - Provide comparison part of sort âą Car - brakingStrategy
- 24. Command Pattern âą Iâm doing a bunch of stuff that I want to be able to keep track of and potentially save and replay later, possibly be able to undo. In order for this to work my object will have to capture everything it needs to know about as far as parameters and what-not in order to be able to run later as well as potentially capturing state so I can get back to where I was before.
- 25. Command Pattern âą Uses: âą Recording Macros âą Multi-level Undo âą Progress Bars âą Transactional Behavior âą Wizards
- 26. Chain of Responsibility âą Each object can take care of something (or not), then it passes to the next object
- 27. Chain of Responsibility Examples âą Loggers - set next logger in chain, each calls the next when it is done âą Managers with purchasing power - if amount is above managerâs level, pass to the next object in the chain
- 28. Observer Pattern âą Notify interested objects of state changes in subject âą Interested objects subscribe to subject âą When subject changes, it calls update on all observers
- 29. MVC - Model View Controller âą Organizational pattern for web dev âą View code contains output âą Model code is for data/business logic âą Controller links model and view code
- 30. Front Controller âą Central entry point for handling requests for web application âą Route all calls through index.php, then ïŹgure out what to do with it
- 31. Adapter Pattern âą Allow interface for an existing class to be used from another interface
- 32. Facade Pattern âą Provide simpliïŹed access to a complex system
- 33. Other Patterns âą Bridge âą Composite âą Decorator âą Front Controller âą Blackboard âą Iterator âą Mediator âą Memento âą Null Object âą SpeciïŹcation âą State âą Template Method âą Visitor âą Abstract Factory âą Prototype