Author: Derick Rethans
Date: 2007-04-20 16:53:39 +0200 (Fri, 20 Apr 2007)
New Revision: 4907
Log:
- Added information about "Dependency Injection"
- Fixed broken documentation in example.
Modified:
docs/guidelines/implementation.txt
Modified: docs/guidelines/implementation.txt
===================================================================
--- docs/guidelines/implementation.txt 2007-04-20 14:52:23 UTC (rev 4906)
+++ docs/guidelines/implementation.txt 2007-04-20 14:53:39 UTC (rev 4907)
@@ -536,6 +536,86 @@
Patterns
========
+Dependency Injection
+--------------------
+
+Some components return objects based on parsed information. This includes the
+Mail and DatabaseSchema components. In some situations it's desirable that the
+classes of the objects can be modified so that the user of a component can use
+his own inherited classes instead. This we call "Dependency Injection".
+
+The configuration of which class to return has to be done with Options_.
+In the option class there needs to be a check if the requested class name
+actually inherits the base class that would be used by default, such as in the
+following code::
+
+ function __set( $propertyName, $propertyValue )
+ {
+ $parentClassMap = array(
+ 'tableClassName' => 'ezcDbSchemaTable',
+ 'fieldClassName' => 'ezcDbSchemaField',
+ 'indexClassName' => 'ezcDbSchemaIndex',
+ 'indexFieldClassName' => 'ezcDbSchemaIndexField',
+ );
+ switch ( $propertyName )
+ {
+ case 'tableClassName':
+ case 'fieldClassName':
+ case 'indexClassName':
+ case 'indexFieldClassName':
+ if ( !is_string( $propertyValue ) )
+ {
+ throw new ezcBaseValueException( $propertyName,
$propertyValue, 'string that contains a class name' );
+ }
+
+ // Check if the passed classname actually implements the
+ // correct parent class. We have to do that with reflection
+ // here unfortunately
+ $parentClass = new ReflectionClass(
$parentClassMap[$propertyName] );
+ $handlerClass = new ReflectionClass( $propertyValue );
+ if ( $parentClassMap[$propertyName] !== $propertyValue &&
!$handlerClass->isSubclassOf( $parentClass ) )
+ {
+ throw new ezcBaseInvalidParentClassException(
$parentClassMap[$propertyName], $propertyValue );
+ }
+
+ $this->properties[$propertyName] = $propertyValue;
+ break;
+
+
+ ... other options ...
+ }
+ }
+
+In case there is only one class name to modify, this can of course be
+simplified to something like the following::
+
+ public function __set( $propertyName, $propertyValue )
+ {
+ switch ( $propertyName )
+ {
+ case 'mailClass':
+ if ( !is_string( $propertyValue ) )
+ {
+ throw new ezcBaseValueException( $propertyName,
$propertyValue, 'string that contains a class name' );
+ }
+
+ // Check if the passed classname actually implements the
+ // correct parent class. We have to do that with reflection
+ // here unfortunately
+ $parentClass = new ReflectionClass( 'ezcMail' );
+ $handlerClass = new ReflectionClass( $propertyValue );
+ if ( 'ezcMail' !== $propertyValue &&
!$handlerClass->isSubclassOf( $parentClass ) )
+ {
+ throw new ezcBaseInvalidParentClassException( 'ezcMail',
$propertyValue );
+ }
+ $this->properties[$propertyName] = $propertyValue;
+ break;
+
+ ... other options ...
+ }
+ }
+
+
Singletons
----------
@@ -761,7 +841,7 @@
/**
* ...
- * @param ezcMailTransportOptions $options
+ * @param ezcFooBarOptions $options
*/
public function __construct( ezcFooBarOptions $options = null )
{
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