Traversable （遍历）接口

(PHP 5, PHP 7, PHP 8)

简介

检测一个类是否可以使用 foreach 进行遍历的接口。

无法被单独实现的基本抽象接口。相反它必须由 IteratorAggregate 或 Iterator 接口实现。

注意:
实现此接口的内建类可以使用 foreach 进行遍历而无需实现 IteratorAggregate 或 Iterator 接口。

注意:
这是一个无法在 PHP 脚本中实现的内部引擎接口。 IteratorAggregate 或 Iterator 接口可以用来代替它。当实现扩展的 Traversable 接口时，确保在 implement 子句中，在名字之前列出了 IteratorAggregate 或者 Iterator。

接口摘要

interface Traversable {

}

这个接口没有任何方法，它的作用仅仅是作为所有可遍历类的基本接口。

add a note

User Contributed Notes 5 notes

down

152

kevinpeno at gmail dot com ¶

11 years ago


While you cannot implement this interface, you can use it in your checks to determine if something is usable in for each. Here is what I use if I'm expecting something that must be iterable via foreach.

<?php
    if( !is_array( $items ) && !$items instanceof Traversable )
        //Throw exception here
?>

down

cobaltbluedw ¶

6 years ago


NOTE:  While objects and arrays can be traversed by foreach, they do NOT implement "Traversable", so you CANNOT check for foreach compatibility using an instanceof check.

Example:

$myarray = array('one', 'two', 'three');
$myobj = (object)$myarray;

if ( !($myarray instanceof \Traversable) ) {
    print "myarray is NOT Traversable";
}
if ( !($myobj instanceof \Traversable) ) {
    print "myobj is NOT Traversable";
}

foreach ($myarray as $value) {
    print $value;
}
foreach ($myobj as $value) {
    print $value;
}

Output:
myarray is NOT Traversable
myobj is NOT Traversable
one
two
three
one
two
three

down

douglas at reith dot com dot au ¶

4 years ago


The PHP7 iterable pseudo type will match both Traversable and array. Great for return type-hinting so that you do not have to expose your Domain to Infrastructure code, e.g. instead of a Repository returning a Cursor, it can return hint 'iterable':
<?php
UserRepository::findUsers(): iterable
?>

Link: http://php.net/manual/en/migration71.new-features.php#migration71.new-features.iterable-pseudo-type

Also, instead of:
<?php
    if( !is_array( $items ) && !$items instanceof Traversable )
        //Throw exception here
?>

You can now do with the is_iterable() method:
<?php
    if ( !is_iterable( $items ))
        //Throw exception here
?>

Link:  http://php.net/manual/en/function.is-iterable.php

down

ajf at ajf dot me ¶

7 years ago


Note that all objects can be iterated over with foreach anyway and it'll go over each property. This just describes whether or not the class implements an iterator, i.e. has custom behaviour.

down

-2

alan dot bem at gmail dot com ¶

3 years ago


Actually you can use `Traversable` within your php scripts - you can use it to enforce iterability on user-land objects.

<?php

interface Stream implements \Traversable {}

class InMemoryStream implements IteratorAggregate, Stream
{
    public function getIterator() {}
}

$stream = new InMemoryStream(); 
?>

In case you'd forgot about implementing `IteratorAggregate` or `Iterator` interfaces, fatal error will be raised when instantiating objects in question.

<?php

interface Stream implements \Traversable {}

class InMemoryStream implements Stream {}

$stream = new InMemoryStream(); // Fatal error: Class InMemoryStream must implement interface Traversable as part of either Iterator or IteratorAggregate in Unknown on line 0
?>

add a note

官方地址：https://www.php.net/manual/en/class.traversable.php

有任何技术问题请点击这里网站运营推广招聘

IT PHP 编程语言 Linux 开发编程科技 Elasticsearch HTML/CSS/XML 网络 JAVA NoSQL 数据库面试 C/C++ Golang Git 算法操作系统正则表达式 Redis 互联网 MySql JavaScript 运维软件国际架构设计 Mac OS TCP/IP Excel Vim Windows Socket Oracle VR MongoDB Python 运营 MemCache 商业硬件电子娱乐设计 nginx 摄影游戏 WordPress HTTP 团建数码电器

php7 安装fileinfo扩展 preg_split — 通过一个正则表达式分隔字符串 php位值,解决 PHP 中 usort 在值相同时改变原始位置的问题 [PHP] inet_pton/inet_ntop IP地址转换函数 array_multisort() 多字段排序 PHPMailer设置utf8 PHPMailer字符集CharSet ADORecordSet对象 adodb手册 PHP 8.1 [鸟哥]PHP_INT_MIN 和 -9223372036854775808 opcache预加载 Composer的Packagist资源 mysql面试题 [鸟哥]PHP FFI详解 - 一种全新的PHP扩展方式 PHP7添加redis扩展 PHP mkdir()写出来的权限与mode值不符合 Packagist / Composer 中国全量镜像 PHP获取指定函数定义在哪个文件中及行号 PHP注释规范利用php soap实现web service

略微加速

PHP官方手册 - 互联网笔记

Traversable （遍历）接口

简介

接口摘要

User Contributed Notes 5 notes