writing extensible applications
TRANSCRIPT
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Writing Extensible Applications
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About meabout me…
Andrey Yatsenco
● PHP Developer at Oro Inc.● 3 years with Symfony ● 6 years with PHP
https://www.facebook.com/yatsencohttps://github.com/anyt
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Writing Extensible Applications
Agenda● Definition● Common solutions● What Symfony offers
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When applications should be extensible?
When you write:● a lot of similar apps● requirements change a lot● a lot of features in one app● open-source
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provide for change (enhancements)● while minimizing impact to existing system
functions.● is a design principle where the
implementation takes future growth into consideration.
● extensions can be through the addition of new functionality or through modification of existing functionality
Extensibility
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Extensible design is to accept that not everything can be designed in advance
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Why code mustbe extensible?
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Typical problems of not extensible apps
● Difficult to replace part of an app● Difficult to scale an application
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Common solutions
● Abstractions and DI● Modular design● Extensions provider● Event-driven architecture
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Common solutions
● Abstractions and DI● Modular design● Extensions provider● Event-driven architecture
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Abstractions and DI
Abstractions: Dependency Injection:
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Common solutions
● Abstractions and DI● Modular design● Extensions provider● Event-driven architecture
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Modular design
Examples:● Symfony● ZF● Yii● Drupal● Joomla● Wordpress● etc.
Naming:● modules● bundles● packages● plugins● service providers● etc.
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Modular design
Make your framework modular:● Symfony HttpKernel component (bundles)
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Modular design
Separating the functionality of a program into independent, interchangeable modules, such that each contains everything necessary to execute only one aspect of the desired functionality.
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Modular design
Bad practices:● High Cohesion● Circular references
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Modular design
Bad practices: How to avoid this?
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Modular design
Bad practices:
How to avoid this?● Event-driven architecture
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Event-driven architecture
● Observer● Mediator
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Event-driven architecture
Observer:
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Event-driven architecture
Mediator
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Modular design
Bad practices:
How to avoid this?● Event-driven architecture● Providing extensions
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Providing extensions
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What Symfony offers?
● Bundles● Service container● Event dispatcher
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What Symfony offers?
Service container● Dependency Injection
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What Symfony offers?
Service container● Overriding classes of services with the
same dependencies with parameters
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What Symfony offers?
Service container● Overriding services in compiler passes with
the same interface or by extending the original one in Compiler Passes
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What Symfony offers?
Service container● Decorating services (new in Symfony 2.5)
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What Symfony offers?
Service container● Providing bundle configuration
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What Symfony offers?
Event dispatcher (mediator pattern)
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What Symfony offers?
You still can provide extension.There is no out of the box solution, because you don’t need it. You can check examples:● Twig● Form
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Conclusion
● Extensions helps you to make addition and modification of your application while minimizing impact to existing functionality.
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Conclusion
Common solutions● Abstractions and DI● Modular design● Extensions provider● Event-driven architecture
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Conclusion
Symfony offers● Bundles● Service container● Event dispatcher
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P.S.
Ideal OO code not the answer, because of performance.You can scale your infrastructure, because it's cheaper than development in some situations but usually not for a long time.
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References
● The Philosophy of Extensible Software● Github - PHP Design Patterns● Wikipedia - Extensibility● Wikipedia - List of software development philosophies● Wikipedia - SOLID● SO - Designing extensible software● Java Docs - Creating Extensible Applications● Symfony Books
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