简介
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 )
}
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
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
逆向思考:
通过调用接口方法来实现对对象属性进行操作,然后使用数组的方式访问
$zhangsan=new Obj();
if ($zhangsan instanceof \ArrayAccess) {
//通过调用接口方法为对象赋值
$zhangsan->offsetSet('name', '张三');
//通过数组方式取值
echo $zhangsan['name'] . PHP_EOL;
//通过调用接口方法取值
echo $zhangsan->offsetGet('name').PHP_EOL;
//通过调用接口方法来判断对象属性是否存在
if (!$zhangsan->offsetExists('age') && !isset($zhangsan['age'])) {
$zhangsan->offsetSet('age', '18');
}
$zhangsan['address']='北京';
//通过调用接口方法来判断对象属性
$zhangsan->offsetUnset('address');
echo $zhangsan['address'] ?? 'address is not exists';
//直接为对象属性赋值(不可行)
$zhangsan->school='Peking University';
echo $zhangsan['school'] ?? 'school is not exists';//school is not exists
}
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