7. PHP pattern design - execution and description tasks_PHP tutorial

7. PHP pattern design ---- execution and description tasks

1. 解析器模式


//解析器内容类
//用于存放表达式的运算结果,并且能根据传入的表达式返回当初记录的结果
class InterpreterContext{
    private $expressionstore=array();
    //将对象放进array里面,索引号是对象ID号
    function replace(Expression $exp,$value){
        $this->expressionstore[$exp->getKey()]=$value;
    }
    function lookup(Expression $exp){
        return $this->expressionstore[$exp->getKey()];
    }
}
abstract class Expression{
    private static $keyCount=0;
    private $key;
    abstract function interpret(InterpreterContext $context);
    //每一个对象都有一个唯一的key
    function getKey(){
        if(!isset($this->key)){
            $this->key=++self::$keyCount;
        }
        return $this->key;
    }
}
//字符串
class LiteralExpression extends Expression{
    private $value;
    function __construct($value){
        $this->value=$value;
    }
    function interpret(InterpreterContext $context){
        $context->replace($this, $this->value);
    }
}
//变量
class VariableExpression extends Expression{
    private $value;
    private $name;
    function __construct($name,$value=null){
        $this->name=$name;
        $this->value=$value;
    }
    function setValue($value){
        $this->value=$value;
    }
    function getKey(){
        return $this->name;
    }
    function interpret(InterpreterContext $context){
        if(!is_null($this->value)){
            $context->replace($this, $this->value);
            //设置为空,可以避免在没有修改value的情况下再次调用该方法的时候,
            //也第二次调用了InterpreterContext::replece
            $this->value=null;
        }
    }
}
//操作符表达式 抽象基类
abstract class OperatorExpression extends Expression{
    //左右操作数
    protected $l_op;
    protected $r_op;
    function __construct(Expression $l_op,Expression $r_op){
        $this->l_op=$l_op;
        $this->r_op=$r_op;
    }
    function interpret(InterpreterContext $context){
        $this->l_op->interpret($context);
        $this->r_op->interpret($context);
        $result_l=$context->lookup($this->l_op);
        $result_r=$context->lookup($this->r_op);
        $this->doInterpret($context, $result_l, $result_r);
    }
    protected abstract function doInterpret(InterpreterContext $context,$result_l,$result_r);
}
//相等表达式
class EqualsExpression extends OperatorExpression{
    //计算后将结果保存进this里...
    protected function doInterpret(InterpreterContext $context,$result_l,$result_r){
        $context->replace($this, $result_l==$result_r);
    }
}
//布尔或表达式
class BooleanOrExpression extends OperatorExpression{
    protected function doInterpret(InterpreterContext $context, $result_l, $result_r){
        $context->replace($this, $result_l || $result_r);
    }
}
//布尔与表达式
class BooleanAndExpression extends OperatorExpression{
    protected function doInterpret(InterpreterContext $context, $result_l, $result_r){
        $context->replace($this, $result_l && $result_r);
    }
}
/*
$context=new InterpreterContext();
$literal=new LiteralExpression("Bob");
$literal->interpret($context);
print $context->lookup($literal);//Bob
$context=new InterpreterContext();
$myvar=new VariableExpression("V","one");
$myvar->interpret($context);
print $context->lookup($myvar);//one
$myothervar=new VariableExpression("V");
$myvar->interpret($context);
print $context->lookup($myvar);//one
*/
//利用上面的代码来检测迷你型语言
//$input equals "4" or $input equals "four"
$context=new InterpreterContext();
//一个没有赋值的变量
$input=new VariableExpression('input');
//定义一个复杂的布尔型变量,初始化的参数被保存在l_op,r_op里面
//注意,此时他们还没有进行相关运算,必须等到调用布尔型变量的interpret()
//之后,布尔型变量里面的参数才会各自调用自身的interpret,形成一个调用栈...
$statement=new BooleanOrExpression(
        new EqualsExpression($input, new LiteralExpression('four')), 
        new EqualsExpression($input, new LiteralExpression('4')));
$statement->interpret($context);
print $context->lookup($statement);
foreach (array('four','4','52') as $val){
    $input->setValue($val);
    print "$val:\n";
    $statement->interpret($context);
    if($context->lookup($statement)){
        print "top marks\n";
    }else{
        print "dunce hat on\n\n";
    }
}
/*four:
top marks
4:
top marks
52:
dunce hat on*/  

2.策略模式
      将类中许多不同操作而且是来自同一个接口的算法,独立起来封装在一个新类中,主类在由分类组合或者聚合而成

//Question类将由Marker聚合而成
abstract class Question{
    protected $prompt;
    protected $marker;
    function __construct($prompt,Marker $marker){
        $this->marker=$marker;
        $this->prompt=$prompt;
    }
    //利用委托实现
    function mark($response){
        return $this->marker->mark($response);
    }
}
class TextQuestion extends Question{
    //处理文本问题特有的操作
}
class AVQuestion extends Question{
    //处理语音问题特有操作
}
//策略对象
//将算法部分独立出来封装在Marker类中....
abstract class Marker{
    protected $test;
    function __construct($test){
        $this->test=$test;
    }
    abstract function mark($response);
}
//MarkLogic语言
class MarkLogicMarker extends Marker{
    protected $engine;
    function __construct($test){
        parent::__construct($test);
    }
    function mark($response){
        //模拟返回true
        return true;
    }
}
//直接匹配
class MatchMarker extends Marker{
    function mark($response){
        return ($this->test==$response);
    }
}
//正则表达式
class RegexpMarker extends Marker{
    function mark($response){
        return (preg_match($this->test, $response));
    }
}
//客户端示例代码
$markers=array(new RegexpMarker("/f.ve/"),
        new MatchMarker("fivev"),
        new MarkLogicMarker('$input equals "five"'));
foreach($markers as $marker){
    print get_class($marker)."\n";
    //新建一个问题,将marker实例传进去
    $question=new TextQuestion("How many beans make five", $marker);
    foreach (array("five","four") as $response){
        print "\t response:$response: ";
        if($question->mark($response)){
            print "well done\n";
        }else{
            print "never mind\n";
        }
    }
}
/*RegexpMarker
     response:five: well done
     response:four: never mind
MatchMarker
     response:five: never mind
     response:four: never mind
MarkLogicMarker
     response:five: well done
     response:four: well done
*/

3 观察者模式

     观察者模式的和兴是把客户元素(观察者)从一个中心类中分离开来.当主体中有事件发生时,观察者必须被通知到!同时观察者和主体类不是通过硬编码实现,而是通过接口组合聚合实现
*问题
// Login类(主体类)
class Login {
    const LOGIN_USER_UNKNOWN = 1;
    const LOGIN_WRONG_PASS = 2;
    const LOGIN_ACCESS = 3;
    private $status = array ();
    // 登录操
    function handleLogin($user, $pass, $ip) {
        $ret=false;
        switch (rand ( 1, 3 )) {
            case 1 :
                $this->setStatus ( self::LOGIN_ACCESS, $user, $ip );
                $ret=ture;
                break;
            case 2 :
                $this->setStatus ( self::LOGIN_WRONG_PASS, $user, $ip );
                $ret=false;
                break;
            case 3 :
                $this->setStatus ( self::LOGIN_USER_UNKNOWN, $user, $ip );
                $ret=false;
                break;
            default:
                $ret=false;
        }
        //如果需要记录IP时
        Logger::logIP($user, $ip, $this->getStatus());
        //如果需要把登录失败的人的IP发送到管理员邮箱时...
        if(!$ret){
            Notifier::mailWarning($user, $ip, $this->getStatus());
        }
        //还需要其他功能时,比如特殊IP需要设置cookie等...
        //需要在这里面一直添加...
        return $ret;
    }
    function setStatus($status, $user, $ip) {
        $this->status = array ($status,$user,$ip);
    }
    function getStatus(){
        return $this->status;
    }
}
class Logger{
    static function logIP($user,$ip,$status){}
}
class Notifier{
    static function mailWarning($user,$ip,$status){}
}
*利用观察者模式,使代码改动少些....
// 主体类的抽象接口
interface Observable{
    //附加
    function attach(Observer $observer);
    //删除
    function detach(Observer $observer);
    //通知
    function notify();
}
// Login类(主体类)
class Login implements Observable{
    const LOGIN_USER_UNKNOWN = 1;
    const LOGIN_WRONG_PASS = 2;
    const LOGIN_ACCESS = 3;
    private $observers;
    private $status = array ();
    // 登录操作
    function handleLogin($user, $pass, $ip) {
        $ret=false;
        switch (rand ( 1, 3 )) {
            case 1 :
                $this->setStatus ( self::LOGIN_ACCESS, $user, $ip );
                $ret=ture;
                break;
            case 2 :
                $this->setStatus ( self::LOGIN_WRONG_PASS, $user, $ip );
                $ret=false;
                break;
            case 3 :
                $this->setStatus ( self::LOGIN_USER_UNKNOWN, $user, $ip );
                $ret=false;
                break;
            default:
                $ret=false;
        }
        //使用观察者模式之后,如果需要增加新功能,只需要在本类中添加观察者实例即可...
        $this->notify();
        return $ret;
    }
    function setStatus($status, $user, $ip) {
        $this->status = array ($status,$user,$ip);
    }
    function getStatus(){
        return $this->status;
    }
    function attach(Observer $observer){
        $this->observers[]=$observer;
    }
    function detach(Observer $observer){
        $newObserver=array();
        foreach ($this->observers as $obs){
            if($obs!==$observer){
                $newObserver[]=$obs;
            }
        }
        $this->observers=$newObserver;
    }
    //通知所有观察者
    function notify(){
        foreach ($this->observers as $bos){
            $bos->update($this);
        }
    }
}
//观察者接口
interface Observer{
    function update(Observable $observable);
}
class SecurityMonitor implements Observer{
    function update(Observable $observable){
        //getStatus()不是Observable接口规定的方法
        $status=$observable->getStatus();
        //对status的判断也涉及到耦合问题
        if($status[0]==Login::LOGIN_WRONG_PASS){
            //发送邮件给管理员
            print __CLASS__.":\t sending mail to sysadmin\n";
        }
    }
}
$login=new Login();
$login->attach(new SecurityMonitor());
$login->handleLogin("coco", "123456", "127.0.0.1");//有可能输出发送消息到管理员

 *改进后的观察者模式

//可观察元素:主体类的基接口
interface Observable{
    //附加
    function attach(Observer $observer);
    //删除
    function detach(Observer $observer);
    //通知
    function notify();
}
// Login类(主体类)
class Login implements Observable{
    const LOGIN_USER_UNKNOWN = 1;
    const LOGIN_WRONG_PASS = 2;
    const LOGIN_ACCESS = 3;
    private $observers;
    private $status = array ();
    // 登录操作
    function handleLogin($user, $pass, $ip) {
        $ret=false;
        switch (rand ( 1, 3 )) {
            case 1 :
                $this->setStatus ( self::LOGIN_ACCESS, $user, $ip );
                $ret=ture;
                break;
            case 2 :
                $this->setStatus ( self::LOGIN_WRONG_PASS, $user, $ip );
                $ret=false;
                break;
            case 3 :
                $this->setStatus ( self::LOGIN_USER_UNKNOWN, $user, $ip );
                $ret=false;
                break;
            default:
                $ret=false;
        }
        //使用观察者模式之后,如果需要增加新功能,只需要在本类中添加观察者实例即可...
        $this->notify();
        return $ret;
    }
    function setStatus($status, $user, $ip) {
        $this->status = array ($status,$user,$ip);
    }
    function getStatus(){
        return $this->status;
    }
    function attach(Observer $observer){
        $this->observers[]=$observer;
    }
    function detach(Observer $observer){
        $newObserver=array();
        foreach ($this->observers as $obs){
            if($obs!==$observer){
                $newObserver[]=$obs;
            }
        }
        $this->observers=$newObserver;
    }
    //通知所有观察者
    function notify(){
        foreach ($this->observers as $bos){
            $bos->update($this);
        }
    }
}
//观察者接口
interface Observer{
    function update(Observable $observable);
}
//Login:观察者超类(用于解决直接在Observer中调用具体的Observable子类造成的风险)
abstract class LoginObserver implements Observer{
    private $login;
    function __construct(Login $login){
        $this->login=$login;
        $this->login->attach($this);
    }
    //该方法在Observable的子类某些方法被调用时触发
    function update(Observable $observable){
        //触发该方法时,传入的参数必须是Login才有效...
        if($this->login===$observable){
             $this->doUpdate($observable);
        }
    }
    abstract function doUpdate(Login $login);
    
}
//改进后的观察者能保证调用的Observable实例方法一定存在
class SecurityMonitor extends LoginObserver{
    function doUpdate(Login $login){
        $status=$login->getStatus();
        //对status的判断也涉及到耦合问题
        if($status[0]==Login::LOGIN_WRONG_PASS){
            //发送邮件给管理员
            print __CLASS__.":\t sending mail to sysadmin\n";
        }
    }
}
//日常记录
class GeneralLogger extends LoginObserver{
    function doUpdate(Login $login){
        $status=$login->getStatus();
        //添加记录到log中
        //...
        print __CLASS__."\t add login data to log\n";
    }
}
//合作伙伴工具类
class PartnershipTool extends LoginObserver{
    function doUpdate(Login $login){
        $status=$login->getStatus();
        //检查IP,如果匹配,则设置cookie...
        //...
        print __CLASS__."\t set cookie if IP matches a list\n";
    }
}
//客户端代码有一点点改变...
$login=new Login();
new SecurityMonitor($login);
new GeneralLogger($login);
new PartnershipTool($login);
$login->handleLogin("coco", "123456", "127.0.0.1");
/*
 * 有可能输出
 *SecurityMonitor:     sending mail to sysadmin
 *GeneralLogger     add login data to log
 *PartnershipTool    set cookie if IP matches a list
 **/

4. 访问者模式
       当使用对象集合时,我们可能需要对结构上每一个单独的组件应用各种操作.这样的操作可以内建于组件本身,毕竟组件内部调用其他组件是最方便的. 
       但是这种方法也存在问题,因为我们并不知道所有可能需要的执行的操作.如果每增加一个操作,就在类中增加一个对于新操作的支持,类就会变得越来越臃肿.访问者模式可以解决这个问题.

//本例是基于"文明"游戏的代码建立而成...
//*战斗单元类
abstract class Unit{
    //深度
    protected $depth=0;
    //攻击强度
    abstract function bombardStrength();
    function getComposite(){
        return null;
    }
    //为访问者模式打造的方法
    function accept(ArmyVisitor $visitor){
        //构建一个根据自己规则定义的方法名,然后交给visitor自身调用
        $method="visit".get_class($this);
        $visitor->$method($this);
    }
    //用于计算Unit在对象树中的深度
    protected function setDepth($depth){
        $this->depth==$depth;
    }
    function getDepth(){
        return $this->depth;
    }
}
//复合抽象类
abstract class CompositeUnit extends Unit{
    protected $units=array();
    //为访问者模式打造的方法
    function accept(ArmyVisitor $visitor){
        //构建一个根据自己规则定义的方法名,然后交给visitor自身调用
        //先调用父类accept(),再遍历调用子元素accept()
        parent::accept($visitor);
        foreach ($this->units as $thisunit){
            $thisunit->accept($visitor);
        }
    }
    //可以不用写bombardStrength()
    function getComposite(){
        return $this;
    }
    //添加单元
    //同时标记节点在对象树中的深度
    function addUnit(Unit $unit){
        if(!empty($unit)){
            if(in_array($unit, $this->units,true)){
                return;
            }
            //可以用下面代码替换in_array()函数
//             foreach ($this->units as $thisunit){
//                 if($thisunit===$unit){
//                     return;
//                 }
//             }
            //计算好深度先...
            $unit->setDepth($this->depth+1);
            array_push($this->units, $unit);
        }
    }
    function removeUnit(Unit $unit){
        $this->units=array_udiff($this->units, array($unit), function ($a,$b){return ($a===$b?0:1);});
    }
    
}
//射手
class Archer extends Unit{
    function bombardStrength(){
        return 4;
    }
}
//激光塔
class LaserCannonUnit extends Unit{
    function bombardStrength(){
        return 44;
    }
}
//军队:由战斗单元组成
class Army extends CompositeUnit{
    //计算总强度
    function bombardStrength(){
        $ret=0;
        foreach ($this->units as $unit){
            $ret+=$unit->bombardStrength();
        }
        return $ret;
    }
    //移动能力,防御能力...省略
}
//运兵船:一个类似军队的单元,它具备10个战斗单元,有攻击力
class TroopCarrier extends CompositeUnit{
    //具备和军队差不多的方法和属性
    function bombardStrength(){
        //Do something...
    }
}
//军队访问者基类
abstract class ArmyVisitor{
    //相关方法待会写...
    //Army可能有多少种Unit,这里就有多少个visit方法...
    //方法命名规则为visit+类名
    //默认的visit
    abstract function visit(Unit $unit);
    function visitArcher(Archer $node){
        $this->visit($node);
    }
    function visitLaserCannonUnit(LaserCannonUnit $node){
        $this->visit($node);
    }
    function visitArmy(Army $node){
        $this->visit($node);
    }
    function visitTroopCarrier(TroopCarrier $node){
        $this->visit($node);
    }
}
//具体的Army访问者类,用于转存文本
class TextDumpArmyVisitor extends ArmyVisitor{
    private $text="";
    function visit(Unit $node){
        $ret="";
        $pad=4*$node->getDepth();
        $ret.=sprintf("%{$pad}s","");
        $ret.=get_class($node).":";
        $ret.="bombard: ".$node->bombardStrength()."\n";
        $this->text.=$ret;
    }
    function getText(){
        return $this->text;
    }
}
//客户端实例代码
$army=new Army();
$army->addUnit(new Archer());
$army->addUnit(new LaserCannonUnit());
$textdump=new TextDumpArmyVisitor();
$army->accept($textdump);
print $textdump->getText();
/*  
 *  Army:bombard: 48
 *  Archer:bombard: 4
 *  LaserCannonUnit:bombard: 44
 */

5. 命令模式
//命令模式
//命令模式最初来源于图形化用户界面设计,但现在广泛应用于企业应用设计,特别促进了控制器(请求和分法处理)
//和领域模型(应用逻辑)的分离.说得更简单一点,命令模式有助于系统更好地进行组织,并易于扩展
//Command可以设计成接口,因为它很简单...
//Commands/Command.php
abstract class Command{
    abstract function execute(CommandContext $context);
}  
require_once("Command.php");
class Registry{
    //一个空类...
    static function getAccessManager(){
        return new AccessManager();
    }
}
class AccessManager{
    function login(){
        return new stdClass();
    }
    function getError(){}
}
class LoginCommand extends Command{
    function execute(CommandContext $context){
        $manager=Registry::getAccessManager();
        $user=$context->get('username');
        $user=$context->get('pass');
        //虚构出来的空类空方法
        $user_obj=$manager->login();
        if(is_null($user_obj)){
            $context->setError($manager->getError());
            return false;
        }
        $context->addParam("user", $user);
        return true;
    }
}  
//CommandContext类用来做任务扩增用,在这儿主要功能是传递数据给Command类
class CommandContext{
    private $params=array();
    private $error="";
    function __construct(){
        $this->params=$_REQUEST;
    }
    function addParam($key,$val){
        $this->params[$key]=$val;
    }
    function get($key){
        return $this->params[$key];
    }
    function setError($error){
        $this->error=$error;
    }
    function getError(){
        return $this->error;
    }
}
//客户端代码(用于创建命令)已经调用者代码
class CommandNotFoundException extends Exception{
    
}
//创建命令的工厂
class CommandFactory{
    private static $dir="Commands";
    //根据参数action,以及类文件存放目录$dir动态创建相应的$action+Command类
    static function getCommand($action='default'){
        //匹配是否出现非法字符(非字母数字下划线)
        if(preg_match('/\W/', $action)){
            throw new Exception("Illegal characters in action");
        }
        $class=ucfirst(strtolower($action)."Command");
        $file=self::$dir.DIRECTORY_SEPARATOR."{$class}.php";
        if(!file_exists($file)){
            throw new CommandNotFoundException("File could not be find !");
        }
        require_once("$file");
        if(!class_exists($class)){
            throw new CommandNotFoundException("Class could not be find !");
        }
        return new $class();
    }
}
//调用者,里面包含一个CommandContext对象实例,用于存放web请求的数据
class Controller{
    private $context;
    function __construct(){
        $this->context=new CommandContext();
    }
    function getContext(){
        return $this->context;
    }
    function process(){
        $cmd=CommandFactory::getCommand($this->getContext()->get('action'));
        if(!$cmd->execute($this->context)){
            //处理失败
            print "Faile in process!";
        }else{
            //处理成功,可以显示相应的视图层
            print "Success in process!";
        }
    }
}
$controller=new Controller();
$context=$controller->getContext();
$context->addParam('action', 'Login');
$context->addParam('user', 'cocos');
$context->addParam('pass', 'tiddles');
//controller执行process方法,需要不理解command的意义.
$controller->process();//Success in process

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