SeekableIterator 接口

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

简介

Seekable 迭代器。

接口摘要

interface SeekableIterator extends Iterator {
/* 方法 */
public seek(int $offset): void
/* 继承的方法 */
}

示例 #1 基础用法

本示例演示了如何创建自定义 SeekableIterator、查找位置和处理无效位置。

<?php
class MySeekableIterator implements SeekableIterator {

private
$position;

private
$array = array(
"first element",
"second element",
"third element",
"fourth element"
);

/* SeekableIterator 接口所需的方法 */

public function seek($position) {
if (!isset(
$this->array[$position])) {
throw new
OutOfBoundsException("invalid seek position ($position)");
}

$this->position = $position;
}

/* Iterator 接口所需的方法 */

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();
}
?>

以上示例的输出类似于:

first element
third element
second element
invalid seek position (10)

目录

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User Contributed Notes 5 notes

up
8
svenr at selfhtml dot org
12 years ago
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
 
}
}

?>
up
-1
info at ensostudio dot ru
3 years ago
Note: use array_key_exists instead isset!
<?php
public function seek($position)
{
   
$position = (int) $position;
    if (!
array_key_exists($position, array_values($this->array))) {
        throw new
OutOfBoundsException('Invalid position to seek: ' . $position);
    }
   
$this->position = $position;
}
?>
up
0
Anonymous
10 years ago
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)");
}
?>
up
-7
martin at smasty dot net
12 years ago
The reflection approach:

<?php

$reflection
= new ReflectionClass('MySeekableIterator');
if(
$reflection->hasMethod('seek'))
  echo
"This class has method seek().";

?>
up
-14
marcin dot kleczek at gmail dot com
13 years ago
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
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