# Ds\Deque::apply

(PECL ds >= 1.0.0)

Ds\Deque::apply — Updates all values by applying a callback function to each value

### 说明

public Ds\Deque::apply(callable `$callback`): void

Updates all values by applying a `callback` function to each value in the deque.

### 参数

`callback`

  callback(mixed `$value`): mixed

  A callable to apply to each value in the deque.

  The callback should return what the value should be replaced by.

### 返回值

没有返回值。

### 示例

示例 #1 Ds\Deque::apply() example

`<?php
$deque = new \Ds\Deque([1, 2, 3]);
$deque->apply(function($value) { return $value * 2; });
print_r($deque);
?>`

以上示例的输出类似于：

    Ds\Deque Object
    (
        [0] => 2
        [1] => 4
        [2] => 6
    )

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