cvs: phpdoc /en/language/oop5 abstract.xml

curt Sun Aug 1 23:12:59 2004 EDT Modified files: /phpdoc/en/language/oop5 abstract.xml Log: Clarify what an abstract class can and cannot do, with example. http://cvs.php.net/diff.php/phpdoc/en/language/oop5/abstract.xml?r1=1.2&r2=1.3&ty=u Index: phpdoc/en/language/oop5/abstract.xml diff -u phpdoc/en/language/oop5/abstract.xml:1.2 phpdoc/en/language/oop5/abstract.xml:1.3 --- phpdoc/en/language/oop5/abstract.xml:1.2 Thu Jul 15 07:19:55 2004 +++ phpdoc/en/language/oop5/abstract.xml Sun Aug 1 23:12:59 2004 @@ -1,13 +1,14 @@ <?xml version="1.0" encoding="iso-8859-1"?> -<!-- $Revision: 1.2 $ --> +<!-- $Revision: 1.3 $ --> <sect1 id="language.oop5.abstract"> <title>Object Abstraction</title> <para> - PHP 5 introduces abstract classes and methods. An abstract - method only declares the method's signature and does not provide an - implementation. A class that contains abstract methods needs to be declared - abstract. + PHP 5 introduces abstract classes and methods. It is not allowed to create + an instance of a class that has been defined as abstract. Any class that + contains at least one abstract method must also be abstract. Methods + defined as abstract simply declare the method's signature they cannot + define the implementation. </para> <example> @@ -15,26 +16,48 @@ <programlisting role="php"> <![CDATA[ <?php + abstract class AbstractClass { - abstract public function test(); + + /* Force Extending class to define this method */ + abstract protected function getValue(); + + /* Common method */ + public function print() { + print $this->getValue(); + } + } -class ImplementedClass extends AbstractClass { - public function test() { - echo "ImplementedClass::test() called.\n"; +class ConcreteClass1 extends AbstractClass { + + protected function getValue() { + return "ConcreteClass1"; } + } -$o = new ImplementedClass; -$o->test(); +class ConcreteClass2 extends AbstractClass { + + protected function getValue() { + return "ConcreteClass2"; + } + +} + +$class1 = new ConcreteClass1; +$class1->print(); + +$class2 = new ConcreteClass2; +$class2->print(); ?> ]]> </programlisting> </example> <para> - Abstract classes cannot be instantiated. Old code that has no user-defined - classes or functions named 'abstract' should run without modifications. + Old code that has no user-defined classes or functions named + 'abstract' should run without modifications. </para> </sect1>