Re: Re: PEAR2 Coding standards, Autoloading and Namespaces

On Apr 8, 2008, at 1:56 AM, Christian Weiske wrote:

I'd like to think outside the box, if you could tell me the solution for following problem: - Package MDB3 - Driver packages MDB3_Sqlite, MDB3_MySql etc How do you load those drivers? Currently it was as easy as checking the existence of $path/MDB2/Driver/Sqlite.php and include the file with that name. If every package uses his own namespace, how do you load such a driver? Where do you store it in the file system so that it can be easily found? Making exceptions to the packagename->namespace rule would work, but defeat the purpose of the whole idea.

Well, I have an answer and its somewhat out of the box, too. :) Rather than having a function that "loads" a driver based that driver being in a specific directory (or based on a specific class name), you can use dependency injection to pass the plugin into the class that will use it. Driver Pattern: class Cache { static function getCache($driver, $options = array()) {

    $file = ‘/drivers/’ . $driver . ‘.php’;
    require_once $file;
    $classname = ucfirst($driver) . 'Cache';
    return new $classname($options);

} } class CacheDriverCommon { protected $options; function __construct($options) {

    $this->options = $options;

} } class FileCache extends CacheDriverCommon {} class FeedFetcher { protected $cache; function __construct($options = array()) {

    $this->cache = Cache::getCache(
      $options[‘driver’],
      $options);

} // Do something with $this->cache later } $fetcher = new FeedFetcher(array('cache'=>'file', 'cache_path'=>'/tmp')); With Dependency Injection: interface Cache {

    // ...

} class FileCache implements Cache { protected $path; function __construct($path) {

    $this->path = $path;

} } class FeedFetcher { protected $cache; function __construct(Cache $cache) {

    $this->cache = $cache;

} } $fetcher = new FeedFetcher(new FileCache(‘/tmp’);); The DI version is more modular, more testable (easier to pass a mock object), and getting rid of the options array has some advantages, such as being easier to document, and autocompletion advice in IDEs becomes available for constructor parameters.