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Ce document utilise Manuel du site Web PHP chinois Libérer
(PHP 5 >= 5.1.0)
The Seekable iterator.
$position
)Example #1 Basic usage
This example demonstrates creating a custom SeekableIterator, seeking to a position and handling an invalid position.
<?php
class MySeekableIterator implements SeekableIterator {
private $position ;
private $array = array(
"first element" ,
"second element" ,
"third element" ,
"fourth element"
);
public function seek ( $position ) {
if (!isset( $this -> array [ $position ])) {
throw new OutOfBoundsException ( "invalid seek position ( $position )" );
}
$this -> position = $position ;
}
public function rewind () {
$this -> position = 0 ;
}
public function current () {
return $this -> array [ $this -> position ];
}
public function key () {
return $this -> position ;
}
public function next () {
++ $this -> position ;
}
public function valid () {
return isset( $this -> array [ $this -> position ]);
}
}
try {
$it = new MySeekableIterator ;
echo $it -> current (), "\n" ;
$it -> seek ( 2 );
echo $it -> current (), "\n" ;
$it -> seek ( 1 );
echo $it -> current (), "\n" ;
$it -> seek ( 10 );
} catch ( OutOfBoundsException $e ) {
echo $e -> getMessage ();
}
?>
以上例程的输出类似于:
first element third element second element invalid seek position (10)
[#1] Anonymous [2013-10-20 00:43:08]
The code above is missing a closing parenthesis.
<?php
if (!isset($this->array[$position]) {
throw new OutOfBoundsException("invalid seek position ($position)");
}
?>
should be
<?php
if (!isset($this->array[$position])) { // close here
throw new OutOfBoundsException("invalid seek position ($position)");
}
?>
[#2] svenr at selfhtml dot org [2011-11-14 16:21:20]
Best method:
<?php
if ($object instanceof SeekableIterator) {
echo "\$object has method seek()";
}
?>
Please, make use of checking if a particular interface has been implemented to assure that the object you are dealing with definately has the methods you are about to use.
This also works as typehinting:
<?php
class foo {
public function doSomeSeeking(SeekableIterator $seekMe) {
$seekMe->seek(10); // will work, otherwise Typehint triggers complaints
}
}
?>
[#3] martin at smasty dot net [2011-05-15 08:01:34]
The reflection approach:
<?php
$reflection = new ReflectionClass('MySeekableIterator');
if($reflection->hasMethod('seek'))
echo "This class has method seek().";
?>
[#4] marcin dot kleczek at gmail dot com [2010-04-15 11:59:06]
Better method:
<?php
$class = 'SeekableIterator';
$findingMethod = 'seek'; // have to be lower chars
$methods = get_class_methods($class);
foreach( $methods as $pVal )
if ( $findingMethod == strtolower($pVal) ) {
echo 'This class has method seek().';
break;
}
}
?>
Best method: http://php.net/manual/en/function.method-exists.php
[#5] dreake at example dot com [2009-06-30 14:38:57]
This example show how to check if some class has method seek() (or another method).
<?php
$class = 'SeekableIterator';
$findingMethod = 'seek'; // have to be lower chars
$methods = get_class_methods($class);
for($i = 0, $ii = count($methods); $i < $ii; $i++){
$sl = strtolower($methods[$i]);
$lowermethods[$i] = $sl;
}
if(in_array($findingMethod,$lowermethods))
echo 'This class has method seek().';
?>