php Iterator 接口详解

使对象可以像数组一样进行foreach循环,实现iterator接口即可

文档:http://php.net/manual/en/class.iterator.php


 

Iterator extends Traversable {

 

/* Methods */

 

abstract public mixed current ( void )

 

abstract public scalar key ( void )

 

abstract public void next ( void )

 

abstract public void rewind ( void )

 

abstract public boolean valid ( void )

}



 

This example demonstrates in which order methods are called when using foreach with an iterator.

<?php
class myIterator implements Iterator {
    private 
$position 0;
    private 
$array = array(
        
"firstelement",
        
"secondelement",
        
"lastelement",
    );  

    public function __construct() {
        
$this->position 0;
    }

    function rewind() {
        
var_dump(__METHOD__);
        
$this->position 0;
    }

    function current() {
        
var_dump(__METHOD__);
        return 
$this->array[$this->position];
    }

    function key() {
        
var_dump(__METHOD__);
        return 
$this->position;
    }

    function next() {
        
var_dump(__METHOD__);
        ++
$this->position;
    }

    function valid() {
        
var_dump(__METHOD__);
        return isset(
$this->array[$this->position]);
    }
}

$it = new myIterator;

foreach($it as $key => $value) {
    
var_dump($key$value);
    echo 
"\n";
}
?>

The above example will output something similar to:

string(18) "myIterator::rewind"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(0)
string(12) "firstelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(1)
string(13) "secondelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(2)
string(11) "lastelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
 


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