设计模式 适配器模式

适配器模式

就是不修改原有类的基础上 加一个中间转换层，以使其符合新需求

说白了，就是对原有类的扩展，怎么扩展，继承呗

例如下：

<?php

//最原始的错误处理
class Error {
    public $_error;

    public function __construct($error) {
        $this->_error = $error;
    }

    public function getError() {
        return $this->_error;
    }
}

class Log {
    public $errObj;

    public function __construct(Error $obj) {
        $this->errObj = $obj;
    }

    public function writeLog() {
         fwrite(STDERR, $this->errObj->getError());
    }
}

$err = new Error('1:wrong!');

$log = new Log($err);
$log->writeLog();

//需求变了，本着那啥和啥的原则，类是不能轻易改动的....
class LogCsv{
    public $csvFile = 'log.txt';

    public $errObj;

    public function __construct(Error $obj)
    {
        $this->errObj = $obj;
    }

    public function writeLog()
    {
        $line = '';
        $line .= $this->errObj->getNum();
        $line .=' ';
        $line .= $this->errObj->getText();

        file_put_contents($this->csvFile, $line);
    }
}

//错误处理适配器
class ErrorAdapter extends Error{
    public $num;
    public $text;

    public function __construct($error)
    {
        $arr = explode(':', $error);
        $this->num = $arr[0];
        $this->text = $arr[1];
    }

    public function getNum()
    {
        return $this->num;
    }
    public function getText()
    {
        return $this->text;
    }
}
$err = new ErrorAdapter('1:wrong!');

$log = new LogCsv($err);
$log->writeLog();