如何使用codeigniter实现工厂模式？

<?php
class Factory {
    public function createObject($type) {
        switch ($type) {
            case 'TypeA':
                return new TypeA();
            case 'TypeB':
                return new TypeB();
            // 添加更多的类型...
            default:
                throw new Exception('Invalid type specified');
        }
    }
}

<?php
interface MyInterface {
    public function doSomething();
}

class TypeA implements MyInterface {
    public function doSomething() {
        // TypeA的具体实现
    }
}

class TypeB implements MyInterface {
    public function doSomething() {
        // TypeB的具体实现
    }
}

<?php
class MyController extends CI_Controller {
    public function index() {
        $factory = new Factory();
        $objectA = $factory->createObject('TypeA');
        $objectB = $factory->createObject('TypeB');
        
        // 使用创建的对象进行操作
        $objectA->doSomething();
        $objectB->doSomething();
    }
}