WordPress: To OOP or not to OOP

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To OOP or not to OOP Nikolay Bachiyski, WordCamp Europe 2013

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Nikolay

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Automattic

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http://extrapolate.me/ @nikolayb github://nb

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Next 25 minutes:

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0.Why should we care?

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1. How WordPress developers see OOP

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2. Better OOP

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0. Why should we care?

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WordPress is BIG

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120K Lines of PHP

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Needs some structure Lines of PHP

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Structure

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No Structure

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Not many rules

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Each small piece is easy to understand

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Hard to change & improve

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Impossible to understand deeply

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Structure = Modules + Communication

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Structure → Code

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Choices in PHP: Procedural and OOP

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Procedural

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↑ Perceived simplicity

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↓ Hard to hide implementation

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↓ Prefix all the things (<5.3)

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↓ Data sharing using globals only

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↓ Hard to test

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OOP

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↓ Perceived complicatedness

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1. How WordPress developers see OOP

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A big reason WP is so popular is because it is not infatuated with the latest, greatest developer lust objects… “

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One of the biggest problems I've found with OOP is that it forces the developer to bake in structure long before the developer actually understands what that structure should be… “

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Classes==Good

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OOP == Bad

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One of the biggest problems I've found with OOP is that it forces the developer to bake in structure long before the developer actually understands what that structure should be… “

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One of the biggest problems I've found with OOP is that it forces the developer to bake in structure long before the developer actually understands what that structure should be… “

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Forces = always happens?

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Building Useful Abstractions is HARD

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Very Hard

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Either refuse responsibility

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Or try

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Fail

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Learn

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Try again

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Fail better

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Succeed

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OOP can be good

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Do one thing, do it well

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class WP_Screen { function get( $hook_name = '' ); function set_current_screen(); function in_admin( $admin = null ); function add_old_compat_help( $screen, $help ); function set_parentage( $parent_file ); function add_option( $option, $args = array() ); function get_option( $option, $key = false ); function get_help_tabs(); function get_help_tab( $id ); function add_help_tab( $args ); function remove_help_tab( $id ); function remove_help_tabs(); function get_help_sidebar(); function set_help_sidebar( $content ); function get_columns(); function render_screen_meta(); function show_screen_options(); function render_screen_options(); function render_screen_layout(); function render_per_page_options(); }

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Responsible for or Represents a

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No And’s, Or’s, or But’s

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Short!

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The big idea is “messaging” [...] The key in making great and growable systems is much more to design how its modules communicate rather than what their internal properties and behaviors should be. “

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Innocuous inheritance

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WP_Image_Editor

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WP_Image_Editor_Imagick extends WP_Image_Editor

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WP_Image_Editor_GD extends WP_Image_Editor

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Common logic in all subclasses

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if ( ! $this->make_image( $filename, 'imagejpeg', array( $image, $filename, apply_filters( 'jpeg_quality', $this- >quality, 'image_resize' ) ) ) ) $this->image->setImageCompressionQuality ( apply_filters( 'jpeg_quality', $quality, 'image_resize' ) ); GD: ImageMagick:

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GD: ImageMagick: protected function update_size( $width = null, $height = null ) { … return parent::update_size( $width, $height ); } protected function update_size( $width = null, $height = null ) { … return parent::update_size( $width, $height ); }

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Change in interface = change in every subclass

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How to spot?

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IS-A vs. HAS-A/USES

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Inheritance for reuse

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Gravatar widget is a WP Widget ✅✓

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ImagickMagick is an Image Editor

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WP Image Editor uses ImagickMagick

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WP Image Editor uses GD

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WP Image Editor has an image

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Composition

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$this->engine = new WP_Image_Engine_GD(); $this->engine = new WP_Image_Engine_ImageMagick(); $this->image = $this->engine->load( $filename ); $new_size = $this->image->update_size();

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function save( $filename = null, $mime_type = null ) { … $jpeg_quality = apply_filters( 'jpeg_quality', … ); $this->image->save( $filename, $mime_type, array( 'jpeg_quality' => $jpeg_quality ) ); … }

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What to remember?

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Communication between modules is everything

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Structure is hard

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We can’t get better without trying and failing first

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Growing Object-Oriented Software, Guided by Tests http://www.growing-object-oriented-software.com/