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eZ Components 2007.1.1

Base

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Introduction

The Base component provides the basic functionality, such as autoloading, that all eZ Components need to function properly. The Base component needs to be loaded specifically. Base can also autoload external class repositories from outside the eZ Components.

Aside from the autoload functionality, the Base component also contains a number of generic Exception classes that all inherit from the ezcBaseException class.

Installation

The installation and configuration of the eZ Components environment is described in a separate article. Please refer to the Components Introduction for instructions on installation and configuration of the eZ Components library and the Base component.

Usage

Debugging

By default the ezcBase component's autoload mechanism will not throw an exception when an autoload class can not be found. In some cases (during development) it is useful to have an exception with detailed information about which autoload files where search for, and in which directories. ezcBase supports an option that enables this behavior:

  1. <?php
  2. $options = new ezcBaseAutoloadOptions;
  3. $options->debug true;
  4. ezcBase::setOptions$options );
  5. ?>


Preloading

The default autoload policy of the eZ Components is to load every class file on demand only. It is also possible to load all classes of one component at the same time, when one of the component's classes is requested for the first time. You can change this behavior with the "preload" option that is available through the ezcBaseAutoloadOptions option class. You can turn preloading on with:

  1. <?php
  2. $options = new ezcBaseAutoloadOptions;
  3. $options->preload true;
  4. ezcBase::setOptions$options );
  5. ?>


Please note that preloading will not be done for Exception classes.

Adding class repositories located outside eZ Components to autoload system

It can be useful to add repositories of user-defined classes to the eZ Components autoload system. The ezcBase::addClassRepository() method can be used to perform this task. You need to arrange the desired external classes in a class repository. That is, make sure that classes and corresponding *_autoload.php files are named and placed according to the explanations below. After they are in the proper structure, you can call addClassRepository() with the proper parameters before you use the external classes. External classes will then be loaded by autoload system.

ezcBase::addClassRepository() takes two arguments:

  • $basePath is the base path for the whole class repository.
  • $autoloadDirPath is the path where autoload files for this repository are found.

The paths in the autoload files are not relative to the package directory as specified by the $basePath argument. In other words, class definition files will only be searched for in the location $autoloadDirPath.

Consider the following example:

  • There is a class repository stored in the directory "./repos".
  • Autoload files for this repository are stored in "./repos/autoloads".
  • There are two components in this repository: "Me" and "You".
  • The "Me" component has the classes "erMyClass1" and "erMyClass2".
  • The "You" component has the classes "erYourClass1" and "erYourClass2".

In this case, you need to create the following files in "./repos/autoloads". Note that the prefix to _autoload.php ("my" and "your") in the filename is the first part of the classname (excluding the lowercase classname prefix - "er").

Content of my_autoload.php:

  1. <?php
  2.     return array (
  3.         'erMyClass1' => 'Me/myclass1.php',
  4.         'erMyClass2' => 'Me/myclass2.php',
  5.     );
  6. ?>

Content of your_autoload.php:

  1. <?php
  2.       return array (
  3.            'erYourClass1' => 'You/yourclass1.php',
  4.            'erYourClass2' => 'You/yourclass2.php',
  5.        );
  6. ?>

The directory structure for the external repository is then:

./repos/autoloads/my_autoload.php
./repos/autoloads/your_autoload.php
./repos/Me/myclass1.php
./repos/Me/myclass2.php
./repos/You/yourclass1.php
./repos/You/yourclass2.php

To use this repository with the autoload mechanism, use the following code:

  1. <?php
  2. require_once 'tutorial_autoload.php';
  3. 
  4. ezcBase::addClassRepository'./repos''./repos/autoloads' );
  5. $myVar1 = new erMyClass2();
  6. $myVar1->toString();
  7. $yourVar1 = new erYourClass1();
  8. $yourVar1->toString();
  9. ?>

The above code will output:

Class 'erMyClass2'
Class 'erYourClass1'

Lazy initialization

Lazy initialization is a mechanism to load and configure a component, only when it is really used in your application. This mechanism saves time for parsing the classes and configuration, when the component is not used at all during one request. The implementation in ezcBaseInit may be reused by other applications and components, like the following example will show.

  1. <?php
  2. require_once 'tutorial_autoload.php';
  3. 
  4. // Create a custom class implementing the singleton pattern
  5. class customSingleton
  6. {
  7.     protected static $instance;
  8. 
  9.     public static function getInstance()
 10.     {
 11.         if ( self::$instance === null )
 12.         {
 13.             self::$instance = new customSingleton();
 14.             ezcBaseInit::fetchConfig'customKey'self::$instance );
 15.         }
 16. 
 17.         return self::$instance;
 18.     }
 19. }
 20. 
 21. // Implement your configuration class
 22. class customSingletonConfiguration implements ezcBaseConfigurationInitializer
 23. {
 24.     public static function configureObjectcustomSingleton $object )
 25.     {
 26.         echo "Configure customSingleton.\n";
 27.         $object->value 42;
 28.     }
 29. }
 30. 
 31. // Register for lazy initilization
 32. ezcBaseInit::setCallback'customKey''customSingletonConfiguration' );
 33. 
 34. // Configure on first initilization
 35. $object customSingleton::getInstance();
 36. var_dump$object->value );
 37. 
 38. ?>

The example shows a random class implementing the singleton pattern, which may be some database connection handler, or anything similar in your case. The getInstance() method shows a typical PHP 5 implementation except the additional line 14, which checks, if a configuration callback was provided earlier and configures the newly created instance. If no configuration callback was provided, nothing will happen. The customKey is used to receive the right callback from ezcBaseInit and needs to be known by the user, who wants to define a configuration callback for your class.

In line 32 the class used to configure your instance on creation is defined. The first parameter is the key used earlier in the getInstance method, to reference the right class, and the second parameter is the name of your configuration class.

The configuration class beginning in line 22 just needs to implement the ezcBaseConfigurationInitializer interface, which defines one method: configureObject(). This method will be called with the object to configure as a single parameter. In the example, a new public property on the customSingleton instance is created, which will be echo'd later to show the success of the configuration.

The configuration itself will not happen before the actual instance is created in line 35 performing the static call on customSingleton::getInstance(). The var_dump() in the following line shows, that the property value is set and contains the earlier set value (int) 42.

Last updated: Wed, 28 Nov 2007