SPL之AccessArray

<?php

/**
 * Class MyArrayAccess
 * 提供像访问数组一样访问对象的能力的接口
 */
class MyArrayAccess implements ArrayAccess
{
    private $container;

    public function __construct(Array $arr)
    {
        $this->container = $arr;
    }

    // 某键是否存在 返回布尔值
    public function offsetExists($offset)
    {
        var_dump(__METHOD__);
        return isset($this->container[$offset]);
    }

    // 获取键对应的值 返回值mixed
    public function offsetGet($offset)
    {
        var_dump(__METHOD__);
        return isset($this->container[$offset]) ? $this->container[$offset] : null;
    }

    // 赋值
    public function offsetSet($offset, $value)
    {
        if (is_null($offset)) {
            $this->container[] = $value;
        } else {
            $this->container[$offset] = $value;
        }
        var_dump(__METHOD__);
    }

    // 删除键值
    public function offsetUnset($offset)
    {
        unset($this->container[$offset]);
        var_dump(__METHOD__);
    }


}

运行：

string(27) "MyArrayAccess::offsetExists"
bool(true)
string(24) "MyArrayAccess::offsetGet"
int(2)
string(26) "MyArrayAccess::offsetUnset"
string(27) "MyArrayAccess::offsetExists"
bool(false)
string(24) "MyArrayAccess::offsetSet"
string(24) "MyArrayAccess::offsetGet"
string(7) "A value"
string(24) "MyArrayAccess::offsetGet"
A valuestring(24) "MyArrayAccess::offsetSet"
string(24) "MyArrayAccess::offsetSet"
string(24) "MyArrayAccess::offsetSet"
object(MyArrayAccess)#1 (1) {
  ["container":"MyArrayAccess":private]=>
  array(6) {
    ["one"]=>
    int(1)
    ["three"]=>
    int(3)
    ["two"]=>
    string(7) "A value"
    [0]=>
    string(8) "Append 1"
    [1]=>
    string(8) "Append 2"
    [2]=>
    string(8) "Append 3"
  }
}

<?php

/**
 * 单例
 * 四私一公
 */
trait Singleton
{
    static private $instance;

    private function __construct()
    {

    }

    private function __clone()
    {

    }

    private function __wakeup()
    {

    }

    static public function getInstance()
    {
        if (is_null(static::$instance)) {
            $class = new ReflectionClass(get_called_class());
            static::$instance = $class->newInstanceWithoutConstructor();
            $method = $class->getConstructor();
            $method->setAccessible(true);
            $method->invokeArgs(static::$instance, func_get_args());
        }
        return static::$instance;
    }
}

/**
 * 对象当数组用
 */
class myAccess implements ArrayAccess
{
    use Singleton;

    private $dataSource = [];

    /**
     * 可返回任意类型
     */
    public function offsetGet($offset)
    {
        var_dump(__METHOD__);
        return $this->dataSource[$offset] ?? null;
    }

    /**
     * 无返回值
     */
    public function offsetSet($offset, $value)
    {
        var_dump(__METHOD__);
        $this->dataSource[$offset] = $value;
    }

    /**
     * 返回布尔值
     * 如果用empty()检测且返回值为true，则自动调用offsetGet
     */
    public function offsetExists($offset)
    {
        var_dump(__METHOD__);
        return isset($this->dataSource[$offset]);
    }

    /**
     * 无返回值
     */
    public function offsetUnset($offset) 
    {
        var_dump(__METHOD__);
        unset($this->dataSource[$offset]);
    }
}

// use
echo '<pre>';

$obj = myAccess::getInstance();
$obj['name'] = 'tom';
isset($obj['name']);
empty($obj['name']);
unset($obj['name']);
var_dump($obj);