简单工厂模式实例与讲解

abstract class ApptEncoder{
abstract function encode();
}

class BloggsApptEncoder extends ApptEncoder{
function encode(){
return 'this is bloggs object';
}
}

class MegaApptEncoder extends ApptEncoder{
function encode(){
return 'this is mega object';
}
}

class CommsManager{
const BLOGGS = 1;
const MEAG = 2;

private $mode = 1;

function __construct($mode){
$this->mode;
}

function getAppEncoder(){
switch ($this->mode){
case (self::BLOGGS):
return new BloggsApptEncoder();
case (self::MEAG):
return new MegaApptEncoder();
}
}
}

$comms = new CommsManager(CommsManager::MEAG);
$apptEncoder = $comms->getAppEncoder();
print_r($apptEncoder->encode());    //输出：this is bloggs object

以上属于典型的简单工厂模式，可以适用于简单的运行模式，存在一定的缺陷，当我们需要在CommsManager中新增一个模式方法时，我们不得不再次进行模式的判断，CommsManager如下（我们新增了getHeaderText）：

class CommsManager{
const BLOGGS = 1;
const MEAG = 2;

private $mode = 1;

function __construct($mode){
$this->mode;
}

function getAppEncoder(){
switch ($this->mode){
case (self::BLOGGS):
return new BloggsApptEncoder();
case (self::MEAG):
return new MegaApptEncoder();
}
}

function getHeaderText(){
switch ($this->mode){
case (self::BLOGGS):
return 'this is bloggs headerText';
case (self::MEAG):
return 'this is meag headerText';
}
}
}

从上面我们可以看出，我们使用了重复的代码判断条件，我们可以对此进行简化和进一步的改进，也就是我们的工厂方法模式