ArrayAccess（数组式访问）接口

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简介

提供像访问数组一样访问对象的能力的接口。

接口摘要

ArrayAccess {

abstract public boolean offsetExists ( mixed $offset )

abstract public mixed offsetGet ( mixed $offset )

abstract public void offsetSet ( mixed $offset , mixed $value )

abstract public void offsetUnset ( mixed $offset )

}

Example #1 Basic usage

  <?php
 class  obj  implements  arrayaccess  {
    private  $container  = array();
    public function  __construct () {
         $this -> container  = array(
             "one"    =>  1 ,
             "two"    =>  2 ,
             "three"  =>  3 ,
        );
    }
    public function  offsetSet ( $offset ,  $value ) {
        if ( is_null ( $offset )) {
             $this -> container [] =  $value ;
        } else {
             $this -> container [ $offset ] =  $value ;
        }
    }
    public function  offsetExists ( $offset ) {
        return isset( $this -> container [ $offset ]);
    }
    public function  offsetUnset ( $offset ) {
        unset( $this -> container [ $offset ]);
    }
    public function  offsetGet ( $offset ) {
        return isset( $this -> container [ $offset ]) ?  $this -> container [ $offset ] :  null ;
    }
}

 $obj  = new  obj ;

 var_dump (isset( $obj [ "two" ]));
 var_dump ( $obj [ "two" ]);
unset( $obj [ "two" ]);
 var_dump (isset( $obj [ "two" ]));
 $obj [ "two" ] =  "A value" ;
 var_dump ( $obj [ "two" ]);
 $obj [] =  'Append 1' ;
 $obj [] =  'Append 2' ;
 $obj [] =  'Append 3' ;
 print_r ( $obj );
 ?>

以上例程的输出类似于：

bool(true)
int(2)
bool(false)
string(7) "A value"
obj Object
(
    [container:obj:private] => Array
        (
            [one] => 1
            [three] => 3
            [two] => A value
            [0] => Append 1
            [1] => Append 2
            [2] => Append 3
        ))

ArrayAccess::offsetExists — 检查一个偏移位置是否存在
ArrayAccess::offsetGet — 获取一个偏移位置的值
ArrayAccess::offsetSet — 设置一个偏移位置的值
ArrayAccess::offsetUnset — 复位一个偏移位置的值

用户评论:

[#1] kaRemovTihsjouni at gmAndTihsaildot com [2015-06-30 15:03:32]

reset() method may not work as you expect with ArrayAccess objects.

Using reset($myArrayAccessObject) returns the first property from $myArrayAccessObject, not the first item in the items array.

If you want to use the reset() method to return the first array item, then you can use the following simple workaround:

<?php class MyArrayAccessObject implements Iterator, ArrayAccess, Countable { protected $first = null; //WARNING! Keep this always first. protected $items = null; private function supportReset() { $this->first = reset($this->items); //Support reset(). } // ... public function offsetSet($offset, $value) { if ($offset === null) { $this->items[] = $value; } else { $this->items[$offset] = $value; } $this->supportReset(); } } ?>

Finally, call $this->supportReset() in the end of all methods that change the internal $items array, such as in offsetSet(), offsetUnset() etc.

This way, you can use the reset() method as normally:

<?php $firstArrayItem = reset($myArrayAccessObject); ?>

[#2] php at lanar dot com dot au [2014-01-27 01:35:22]

Objects implementing ArrayAccess do not support the increment/decrement operators ++ and --, unlike array() and ArrayObject()

<?php class MyArray implements ArrayAccess { // offsetSet, offsetGet etc implemented } $x = new MyArray() ; $x[0] = 0 ; $x[0]++ ; //error 'Indirect modification of overloaded element has no effect' $x[0] += 1 ; // this works OK. ?>

[#3] Yousef Ismaeil Cliprz [2013-12-11 07:38:24]

<?php class ArrayAndObjectAccess implements ArrayAccess { private $data = []; public function &__get ($key) { return $this->data[$key]; } public function __set($key,$value) { $this->data[$key] = $value; } public function __isset ($key) { return isset($this->data[$key]); } public function __unset($key) { unset($this->data[$key]); } public function offsetSet($offset,$value) { if (is_null($offset)) { $this->data[] = $value; } else { $this->data[$offset] = $value; } } public function offsetExists($offset) { return isset($this->data[$offset]); } public function offsetUnset($offset) { if ($this->offsetExists($offset)) { unset($this->data[$offset]); } } public function offsetGet($offset) { return $this->offsetExists($offset) ? $this->data[$offset] : null; } } ?>

Usage

<?php $foo = new ArrayAndObjectAccess(); // Set data as array and object $foo->fname = 'Yousef'; $foo->lname = 'Ismaeil'; // Call as object echo 'fname as object '.$foo->fname."\n"; // Call as array echo 'lname as array '.$foo['lname']."\n"; // Reset as array $foo['fname'] = 'Cliprz'; echo $foo['fname']."\n"; ?>

[#4] ivan dot dossev at gmail dot com [2013-04-20 07:09:06]

Sadly you cannot assign by reference with the ArrayAccess (at least in PHP 5.3.23)
It's too bad there is no syntax for optionally passing variables by reference to functions (a feature in retro PHP).
That option would have let ArrayAccess fully mimic the functionality of normal array assignments:

<?php $var = 'hello'; $arr = array(); $arr[0] = $var; $arr[1] = &$var; $var = 'world'; var_dump($arr[0], $arr[1]); // string(5) "hello" // string(5) "world" ?>

Declaring "function offsetSet($offset, &$value)" will cause a fatal error.
So to assign by ref you can use an ugly function call, for example:

<?php class obj implements ArrayAccess { // ... ArrayAccess example code ... public function &offsetSetRef($offset, &$value) { if (is_null($offset)) { $this->container[] = &$value; } else { $this->container[$offset] = &$value; } return $value; // should return in case called within an assignment chain } } $var = 'hello'; $obj = new obj(); $obj[0] = $var; //$obj[1] = &$var; // Fatal error: Cannot assign by reference to overloaded object $obj->offsetSetRef(1, $var); // the work around $var = 'world'; var_dump($obj[0], $obj[1]); // string(5) "hello" // string(5) "world" ?>

[#5] Hayley Watson [2013-03-31 00:25:39]

The indexes used in an ArrayAccess object are not limited to strings and integers as they are for arrays: you can use any type for the index as long as you write your implementation to handle them. This fact is exploited by the SplObjectStorage class.

[#6] jojor at gmx dot net [2012-12-12 13:08:10]

Conclusion: Type hints \ArrayAccess and array are not compatible.

<?php class MyArrayAccess implements \ArrayAccess { public function offsetExists($offset) { } public function offsetSet($offset, $value) { } public function offsetGet($offset) { } public function offsetUnset($offset) { } } function test(array $arr) { } function test2(\ArrayAccess $arr) { } $arrObj = new MyArrayAccess(); test([]); //result: works! test($arrObj); //result: does NOT work test2([]); //result: does NOT work test2($arrObj); // result: works! ?>

[#7] Per [2011-05-20 02:16:33]

It bit me today, so putting it here in the hope it will help others:
If you call array_key_exists() on an object of a class that implements ArrayAccess, ArrayAccess::offsetExists() wil NOT be called.

[#8] max at flashdroid dot com [2010-04-05 18:49:40]

Objects implementing ArrayAccess may return objects by references in PHP 5.3.0.

You can implement your ArrayAccess object like this:

    class Reflectable implements ArrayAccess {

        public function set($name, $value) {
            $this->{$name} = $value;
        }

        public function &get($name) {
            return $this->{$name};
        }

        public function offsetGet($offset) {
            return $this->get($offset);
        }

        public function offsetSet($offset, $value) {
            $this->set($offset, $value);
        }

        ...

    }

This base class allows you to get / set your object properties using the [] operator just like in Javascript:

    class Boo extends Reflectable {
        public $name;
    }

    $obj = new Boo();
    $obj['name'] = "boo";
    echo $obj['name']; // prints boo

ArrayAccess（数组式访问）接口

简介

接口摘要

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用户评论: