设计模式七：工厂模式

工厂模式：

　　分为简单工厂，方法工厂，和抽象工厂。

一：简单工厂

　　简单工厂的作用是实例化对象，而不需要调用者知道该对象具体对应的子类。

<?php

class MysqlLog{
    public function log(){
        echo '记录Mysql错误'.PHP_EOL;
    }
}

class ErrorLog{
    public function log(){
        echo '记录程序错误'.PHP_EOL;
    }
}

/**
 * 工厂类
 */
class Factory{
    public function make($abstract){
        switch($abstract){
            case 'mysql':
                return new MysqlLog();
            case 'error':
                return new ErrorLog();
        }
    }
}

/**
 * 日志调用类
 */
class Log{
    
    protected $logs;

    public function __construct($abstracts)
    {
        $factory = new Factory();
        foreach($abstracts as $value){
            $this->logs[$value] = $factory->make($value);
        }
    }

    public function write($abstract){
        return $this->logs[$abstract]->log();
    }
}

$log = new Log(['mysql','error']);
$log->write('mysql');
$log->write('error');

二：方法工厂

　　在简单工厂的基础上进行改进，由一个工厂变为多个工厂。

class MysqlLog{
    public function log(){
        echo '记录Mysql错误'.PHP_EOL;
    }
}

class ErrorLog{
    public function log(){
        echo '记录程序错误'.PHP_EOL;
    }
}

/**
 * 工厂类
 */
class MysqlFactory{
    public function make(){
       return new MysqlLog();
    }
}
class ErrorFactory{
    public function make(){
       return new ErrorLog();
    }
}

/**
 * 日志调用类
 */
class Log{
    
    protected $logs;

    public function __construct()
    {
        $this->logs['mysql'] = (new MysqlFactory())->make();
        $this->logs['error'] = (new ErrorFactory())->make();
    }

    public function write($abstract){
        return $this->logs[$abstract]->log();
    }
}

$log = new Log();
$log->write('mysql');
$log->write('error');

三：抽象工厂

　　相对于方法工厂，抽象工厂对外提供的是一个抽象接口。抽象工厂，抽象方法。

<?php
/**
 * 功能抽象类
 */
interface LogInterface{
    public function log();
}

class MysqlLog implements LogInterface{
    public function log(){
        echo '记录Mysql错误'.PHP_EOL;
    }
}

class ErrorLog implements LogInterface{
    public function log(){
        echo '记录程序错误'.PHP_EOL;
    }
}

/**
 * 工厂抽象类
 */
interface LogFactoryInterface {
    public function mysqlMake();

    public function errorMake();
}

class LogFactory implements LogFactoryInterface{
    public function mysqlMake(){
       return new MysqlLog();
    }

    public function errorMake(){
        return new ErrorLog();
     }
}

/**
 * 日志调用类
 */
class Log{
    
    protected $logs;

    public function __construct()
    {
        $logFactory = new LogFactory();
        $this->logs['mysql'] = $logFactory->mysqlMake();
        $this->logs['error'] = $logFactory->errorMake();
    }

    public function write($abstract){
        return $this->logs[$abstract]->log();
    }
}

$log = new Log();
$log->write('mysql');
$log->write('error');