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https://github.com/sigmasternchen/php-doc-en
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9ee9eccf45
Some misses from the first time Signed-off-by: Larry Garfield <larry@garfieldtech.com> Closes GH-329
144 lines
3.3 KiB
XML
144 lines
3.3 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<sect1 xml:id="language.oop5.abstract" xmlns="http://docbook.org/ns/docbook">
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<title>Class Abstraction</title>
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<para>
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PHP has abstract classes and methods.
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Classes defined as abstract cannot be instantiated, and any class that
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contains at least one abstract method must also be abstract.
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Methods defined as abstract simply declare the method's signature;
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they cannot define the implementation.
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</para>
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<para>
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When inheriting from an abstract class, all methods marked abstract in
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the parent's class declaration must be defined by the child class,
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and follow the usual
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<link linkend="language.oop5.inheritance">inheritance</link> and
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<link linkend="language.oop.lsp">signature compatibility</link> rules.
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</para>
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<example>
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<title>Abstract class example</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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abstract class AbstractClass
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{
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// Force Extending class to define this method
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abstract protected function getValue();
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abstract protected function prefixValue($prefix);
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// Common method
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public function printOut() {
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print $this->getValue() . "\n";
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}
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}
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class ConcreteClass1 extends AbstractClass
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{
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protected function getValue() {
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return "ConcreteClass1";
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}
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public function prefixValue($prefix) {
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return "{$prefix}ConcreteClass1";
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}
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}
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class ConcreteClass2 extends AbstractClass
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{
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public function getValue() {
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return "ConcreteClass2";
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}
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public function prefixValue($prefix) {
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return "{$prefix}ConcreteClass2";
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}
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}
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$class1 = new ConcreteClass1;
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$class1->printOut();
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echo $class1->prefixValue('FOO_') ."\n";
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$class2 = new ConcreteClass2;
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$class2->printOut();
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echo $class2->prefixValue('FOO_') ."\n";
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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ConcreteClass1
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FOO_ConcreteClass1
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ConcreteClass2
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FOO_ConcreteClass2
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]]>
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</screen>
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</example>
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<example>
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<title>Abstract class example</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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abstract class AbstractClass
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{
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// Our abstract method only needs to define the required arguments
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abstract protected function prefixName($name);
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}
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class ConcreteClass extends AbstractClass
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{
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// Our child class may define optional arguments not in the parent's signature
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public function prefixName($name, $separator = ".") {
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if ($name == "Pacman") {
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$prefix = "Mr";
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} elseif ($name == "Pacwoman") {
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$prefix = "Mrs";
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} else {
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$prefix = "";
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}
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return "{$prefix}{$separator} {$name}";
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}
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}
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$class = new ConcreteClass;
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echo $class->prefixName("Pacman"), "\n";
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echo $class->prefixName("Pacwoman"), "\n";
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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Mr. Pacman
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Mrs. Pacwoman
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]]>
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</screen>
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</example>
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</sect1>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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