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New iteration documentation.
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@164130 c90b9560-bf6c-de11-be94-00142212c4b1
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Curt Zirzow
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1 changed files with 206 additions and 2 deletions
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<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.1 $ -->
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<!-- $Revision: 1.2 $ -->
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<sect1 id="language.oop5.iterations">
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<title>Object Iteration</title>
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<para>
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.
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PHP 5 provides a way for objects to to be defined so it is possible
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to iterate through a list of items, with, for example a <xref
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linkend="control-structures.foreach" /> statement. By default, all
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public properties will be used for the iteration.
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</para>
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<example>
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<title>Simple Object Iteration</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class MyClass {
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public $var1 = 'value 1';
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public $var2 = 'value 2';
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public $var3 = 'value 3';
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protected $protected = 'protected';
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private $private = 'private';
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}
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$class = new MyClass();
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foreach($class as $key => $value) {
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print "$key => $value\n";
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}
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]]>
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</programlisting>
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<para>
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Will output:
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</para>
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<screen role="php">
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<![CDATA[
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var1 => value 1
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var2 => value 2
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var3 => value 3
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]]>
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</screen>
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</example>
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<para>
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As the output shows, the <xref linkend="control-structures.foreach" />
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iterated through each public variable that is defined. To take it
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a step further you can <varname>implement</varname> one of PHP 5's
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internal <xref linkend="language.oop5.interfaces" /> named
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<varname>Iterator</varname>. This allows the object to decide what
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and how the object will be iterated.
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</para>
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<example>
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<title>Object Iteration implenting Iterator</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class MyIterator implements Iterator {
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private $var = array();
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public function __construct($array) {
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if (is_array($array) ) {
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$this->var = $array;
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}
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}
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public function rewind() {
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echo "rewinding\n";
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reset($this->var);
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}
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public function current() {
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$var = current($this->var);
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echo "current: $var\n";
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return $var;
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}
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public function key() {
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$var = key($this->var);
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echo "key: $var\n";
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return $var;
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}
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public function next() {
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$var = next($this->var);
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echo "next: $var\n";
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return $var;
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}
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public function valid() {
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$var = $this->current() !== false;
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echo "valid: {$var}\n";
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return $var;
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}
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}
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$values = array(1,2,3);
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$it = new MyIterator($values);
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foreach ($it as $a => $b) {
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print "$a: $b\n";
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}
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]]>
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</programlisting>
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<para>
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Will output:
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</para>
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<screen role="php">
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<![CDATA[
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rewinding
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current: 1
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valid: 1
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current: 1
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key: 0
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0: 1
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next: 2
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current: 2
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valid: 1
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current: 2
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key: 1
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1: 2
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next: 3
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current: 3
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valid: 1
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current: 3
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key: 2
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2: 3
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next:
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current:
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valid:
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]]>
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</screen>
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</example>
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<para>
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You can also define your class so that it doesn't have to define
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all the <varname>Iterator</varname> functions by simply implementing
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the PHP 5 <varname>IteratorAggregate</varname> interface.
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</para>
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<example>
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<title>Object Iteration implenting IteratorAggregate</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class MyCollection implements IteratorAggregate {
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private $items = array();
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private $count = 0;
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/* Required definition of interface IteratorAggregate */
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public function getIterator() {
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return new MyIterator($this->items);
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}
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public function add($value) {
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$this->items[$this->count++] = $value;
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}
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}
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$coll = new MyCollection();
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$coll->add('value 1');
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$coll->add('value 2');
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$coll->add('value 3');
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foreach ($coll as $key => $val) {
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echo "key/value: [$key -> $val]\n\n";
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}
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?>
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</pre>
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]]>
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</programlisting>
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<para>
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Will output:
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</para>
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<screen role="php">
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<![CDATA[
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rewinding
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current: value 1
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valid: 1
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current: value 1
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key: 0
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key/value: [0 -> value 1]
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next: value 2
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current: value 2
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valid: 1
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current: value 2
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key: 1
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key/value: [1 -> value 2]
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next: value 3
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current: value 3
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valid: 1
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current: value 3
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key: 2
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key/value: [2 -> value 3]
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next:
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current:
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valid:
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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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