The Secret Sauce For Writing Reusable Code

Everyone knows that you need to write reusable code to be able to grow as a developer, right?

However, most developers struggle to understand how to split up their code to make it truly reusable, so they end up copy-pasting parts of code and modifying as needed, instead of effectively reusing the code that was already written, without a single change.

This session explains the concept of Config files and how they allow you to cleanly separate reusable code from project-specific code.

( This talk was held at WordCamp Netherlands in Utrecht on Oct. 15, 2016: https://2016.netherlands.wordcamp.org/session/the-secret-sauce-for-writing-reusable-code/ )

( Complimentary blog posts: https://www.alainschlesser.com/config-files-for-reusable-code/ )

Transcript

1. The Secret Sauce
   Writing Reusable Code
   Alain Schlesser www.alainschlesser.com
   Software Engineer & WordPress Consultant @schlessera
   

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2. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
   NOTE:
   This talk was held at WordCamp Nederlands in Utrecht on Oct. 15, 2016.
   There’s an (on-going) series of complimentary blog posts:
   https:/
   /www.alainschlesser.com/config-files-for-reusable-code/
   

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3. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
   About The Person In Front Of You
   Born in Luxembourg
   Living in Germany
   Working in the Cloud
   Passionate about:
   Code quality, software architecture, best
   practices, principles, patterns, and
   everything related.
   

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4. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
   What To Expect
   1. General principle that makes
   code reusable
   2. Common way of
   implementing this principle
   

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5. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
   The Problem With Reusable Code…
   

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6. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
   Object-oriented syntax in and
   of itself does not make your
   code reusable.
   

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7. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
   So We Need To Rearrange This…
   

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8. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
   …Into This
   

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9. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
   Design your code so that the
   reusable parts and the project-
   specific parts never intermingle.
   

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10. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    This Easily Allows Us To Go From This…
    

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11. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    …To This
    

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12. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Example Code
    Problem:
    We want to have a reusable
    Greeter class that can show
    different greetings in different
    projects.*
    * Silly example that can still fit on slides
    

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13. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    class Greeter {
    /**
    * @param string $name The name of the person to greet.
    */
    public function greet( $name ) {
    printf( 'Hello %2$s!', $name );
    }
    }
    Mixed Code Types
    

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14. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    class Greeter {
    /**
    * @param string $name The name of the person to greet.
    */
    public function greet( $name ) {
    printf( 'Hello %2$s!', $name );
    }
    }
    = reusable code = project-specific code
    Mixed Code Types
    

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15. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    The reusable class should completely
    ignore where it gets its business
    logic from. It should act on
    whatever gets passed to it.
    à Injection
    

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16. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    class ReusableGreeter {
    /** @var ConfigInterface */
    protected $config;
    /**
    * @param ConfigInterface $config The Config to use.
    */
    public function __construct( ConfigInterface $config ) {
    $this->config = $config;
    }
    /**
    * @param string $name The name of the person to greet.
    */
    public function greet( $name ) {
    $greeting = $this->config->get( 'greeting' );
    printf( '%1$s %2$s!', $greeting, $name );
    }
    }
    

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17. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    class ReusableGreeter {
    /** @var ConfigInterface */
    protected $config;
    /**
    * @param ConfigInterface $config The Config to use.
    */
    public function __construct( ConfigInterface $config ) {
    $this->config = $config;
    }
    /**
    * @param string $name The name of the person to greet.
    */
    public function greet( $name ) {
    $greeting = $this->config->get( 'greeting' );
    printf( '%1$s %2$s!', $greeting, $name );
    }
    }
    = reusable code = project-specific code
    

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18. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Business-specific Code à Config File
    Config File
    Reusable Class
    Business Logic
    

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19. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    // We return a standard PHP array as a result of including
    // this Config file.
    return [
    'greeting' => 'Hello',
    ];
    Basic Config File
    

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20. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    // We return a standard PHP array as a result of including
    // this Config file.
    return [
    'greeting' => 'Hello',
    ];
    = reusable code = project-specific code
    =>
    Basic Config File
    

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21. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Immediate Benefits
    • Separate files
    • Injection
    • Type-hinting
    • Validation
    

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22. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Secondary Benefits
    • Forced modularisation
    • Tested code
    • Collaboration
    

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23. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Source Is Flexible
    As the source should be irrelevant for the
    classes that use the Config data, you can
    combine several files into one, read them
    from a database or network, build them at
    run-time for unit tests, etc…
    

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24. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    // We can prefix a section of a Config, so that one file
    // can be used for multiple classes.
    return [
    'ReusableGreeter' => [
    'greeting' => 'Hello',
    ],
    ];
    Prefix For The Reusable Class
    

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25. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    class Plugin {
    /** @var ConfigInterface */
    protected $config;
    /**
    * @param ConfigInterface $config The Config to use.
    */
    public function __construct( ConfigInterface $config ) {
    $this->config = $config;
    }
    public function run() {
    $greeter = new ReusableGreeter(
    $this->config->getSubConfig( 'ReusableGreeter' )
    );
    $greeter->greet( 'World' );
    }
    }
    

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26. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Config File
    Getting The Config File Into The Reusable Class
    Reusable Class
    Plugin Class
    Business Logic
    Business Logic
    Business Logic
    

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27. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    // We can prefix the entire Config, so that a single file
    // can be shared across several plugins.
    $reusable_greeter = [
    'greeting' => 'Hello',
    ];
    return [
    'Example' => [
    'Greeter' => [
    'ReusableGreeter' => $reusable_greeter;
    ],
    ],
    ];
    Prefix For Multiple Plugins
    

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28. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    namespace Example\Greeter;
    $config = ConfigFactory::create( __DIR__ . 'config/defaults.php' );
    $plugin = new Plugin( $config->getSubConfig( __NAMESPACE__ ) );
    $plugin->run();
    Prefix For Multiple Plugins
    

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29. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Configs & Auto-wiring Injection
    interface DatabaseConfig extends ConfigInterface { }
    class Database {
    /** @var DatabaseConfig */
    protected $config;
    /**
    * @param DatabaseConfig $config The Config to use.
    */
    public function __construct( DatabaseConfig $config ) {
    $this->config = $config;
    }
    }
    

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30. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Domain-Specific Language
    Domain-specific language (noun):
    a computer programming language of limited
    expressiveness focused on a particular domain.
    - Martin Fowler, ThoughtWorks
    

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31. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    PHP Config ... Closures! ( = ~DSL )
    

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32. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Adapted Configs
    Provide defaults and then override with different Configs …
    • for different sites/apps (site_a.php)
    • for different environments (site_a-development.php)
    • for different contexts (unit-tests.php)
    • for specific situations (run-backups.php)
    • …
    

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33. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Site/App-specific Configurations
    config/defaults.php
    config/dt.php
    

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34. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    

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35. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    Config Library
    https://github.com/brightnucleus/config
    My own library:
    Alternatives:
    https://github.com/symfony/config
    symfony/config
    https://github.com/zendframework/zend-config
    zendframework/zend-config
    brightnucleus/config
    

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36. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    “Can You Summarize, Please?”
    • Design for reusability from the get-go
    • Have a clean separation between
    different types of code
    • Config files provide a structured way of
    injecting project-specific logic into
    reusable classes
    

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37. The Secret Sauce For Writing Reusable Code – 15th Octobre 2016– Alain Schlesser
    The End
    I’m Alain Schlesser.
    Follow me on twitter:
    @schlessera
    Or visit my site:
    www.alainschlesser.com
    

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