PHP预定义接口：ArrayAccess

Posted 2020-11-18

简介

• 提供像访问数组一样访问对象的能力的接口。

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接口摘要

ArrayAccess {
/* 方法 */
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 )
}

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目录

• 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

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代码演示

class Obj implements ArrayAccess
{
    private $container = [];

    public function offsetExists($offset): bool
    {
        echo ‘调用‘ . __METHOD__ . ‘方法‘ . php_EOL;
        echo print_r(func_get_args(), true);

        return isset($this->container[$offset]);
    }

    public function offsetGet($offset)
    {
        echo ‘调用‘ . __METHOD__ . ‘方法‘ . PHP_EOL;
        echo print_r(func_get_args(), true);

        return $this->container[$offset] ?? null;
    }

    public function offsetSet($offset, $value)
    {
        echo ‘调用‘ . __METHOD__ . ‘方法‘ . PHP_EOL;
        echo print_r(func_get_args(), true);
        $this->container[$offset] = $value;
    }

    public function offsetUnset($offset)
    {
        echo ‘调用‘ . __METHOD__ . ‘方法‘ . PHP_EOL;
        echo print_r(func_get_args(), true);

        unset($this->container[$offset]);
    }
}

//实例化对象
$zhangsan = new Obj();

//赋值
$zhangsan[‘name‘] = ‘张三‘;//调用Obj::offsetSet方法

//输出
echo $zhangsan[‘name‘] . PHP_EOL;//调用Obj::offsetGet方法

//校验是否存在
isset($zhangsan[‘name‘]) . PHP_EOL;//调用Obj::offsetExists方法

//删除数组单元
unset($zhangsan[‘name‘]);//调用Obj::offsetUnset方法

应用案例演示

实现配置文件信息读取

准备工作:

按照一下给出的目录结构建立文件

./
├── config
│?? ├── app.php
│?? └── database.php
└── config.php

• ./config/app.php

  <?php
  return [
      ‘name‘ => ‘app name‘,
      ‘version‘ => ‘v1.0.0‘
  ];

• ./config/database.php

  <?php
  return [
      ‘mysql‘ => [
          ‘host‘ => ‘localhost‘,
          ‘user‘ => ‘root‘,
          ‘password‘ => ‘12345678‘
      ]
  ];

• ./config.php

<?php

namespace Config;

final Class Config implements ArrayAccess
{
    private $config = [];
    private static $instance = null;
    private $path = null;

    private function __construct()
    {
        $this->path = __DIR__ . ‘/config/‘;
    }

    //单例模式获取实例
    public static function getInstance()
    {
        if (!self::$instance instanceof self) {
            self::$instance = new self;
        }
        return self::$instance;
    }

    //防止被克隆
    private function __clone()
    {
    }

    public function offsetExists($offset)
    {
        return isset($this->config[$offset]);
    }

    public function offsetGet($offset)
    {
        if (!isset($this->config[$offset]) || empty($this->config[$offset])) {
            //装载配置文件
            $this->config[$offset] = require $this->path . $offset . ‘.php‘;
        }
        return $this->config[$offset];
    }

    public function offsetSet($offset, $value)
    {
        throw new Exception(‘不提供设置配置‘);
    }

    public function offsetUnset($offset)
    {
        throw new Exception(‘不提供删除配置‘);
    }
}

$config = Config::getInstance();

//获取app.php 文件的 name
echo $config[‘app‘][‘name‘].PHP_EOL; //app name

//获取database.php文件mysql的user配置
echo $config[‘database‘][‘mysql‘][‘user‘].PHP_EOL; // root