实施工厂模式的正确方法是什么？ [英] What is the right way to implement factory pattern?

问题描述

我只是想知道这是否是在PHP中创建对象和实现工厂模式的正确方法。我知道我们有工厂方法模式和抽象工厂模式，但是我们有一个如下所示的模式
http://noondreams.com/shared/data/pages/images/Factory.png ？

I just wonder if this is the right way to create objects and implement the factory pattern in PHP. I know we have factory method pattern and Abstract factory pattern, but do we have a pattern like the following http://noondreams.com/shared/data/pages/images/Factory.png ?

class Factory
{
 public function make($format)
 {
    switch($format)
    {
        case Source::Assocs:
            return new \Source\Formats\Assocs();
        case Source::XML
            return new \Source\Formats\XML();
        //Some other formats
    }
 }
}

推荐答案

不，这不是一个真正的工厂模式。工厂模式看起来更像这样：

No, this isn't really a factory pattern. The factory pattern would look more like this:

<?php
abstract class File
{
    public static function createFromFile($filename)
    {
        $extension = /* get file extension */;

        switch ($extension)
        {
            case 'xml':
                return new XmlFile($filename);
                break;
            case 'php':
                return new PhpFile($filename);
                break;
        }

        throw new \InvalidArgumentException();
    }
}

class XmlFile extends File
{

}

class PhpFile extends File
{

}

注意抽象类如何创建具体的类可以扩展它，而不用担心用户可能返回的各种类型。

Notice how the abstract class is creating instances of concrete classes which extend it without the user having to worry about the various types it may return.

注意：在一个真实情况下，你会不要使用switch语句，但可能是反射或其他各种技巧，因为抽象类不会知道它的所有子类。

Note: in a real scenario, you wouldn't use a switch statement, but likely reflection or various other techniques since the abstract class wouldn't know all of it's child classes.

可能看起来更像这样：

That may look more like this:

<?php
abstract class File
{
    public static function createFromFile($filename)
    {
        $extension = /* get file extension */;
        $extension = ucfirst($extension);

        $reflection = new ReflectionClass($extension . 'File');
        return $reflection->newInstanceArgs(array($filename));
    }
}

class XmlFile extends File
{

}

class PhpFile extends File
{

}

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