php实现工厂模式
<?php//工厂模式的最大优点在于创建对象上面,就是把创建对象的过程封装起来,这样随时可以产生一个新的对象。//减少代码进行复制粘帖,耦合关系重,牵一发动其他部分代码。//通俗的说,以前创建一个对象要使用new,现在把这个过程封装起来了。//假设不使用工厂模式:那么很多地方调用类a,代码就会这样子创建一个实例:new a(),假设某天需要把a类的名称修改,意味着很多调用的代码都要修改。//工厂模式的优点就在创建对象上。//工厂模式的优点就在创建对象上。建立一个工厂(一个函数或一个类方法)来制造新的对象,它的任务就是把对象的创建过程都封装起来,//创建对象不是使用new的形式了。而是定义一个方法,用于创建对象实例。//每个类可能会需要连接数据库。那么就将连接数据库封装在一个类中。以后在其他类中通过类名://为什么引入抽象的概念?//想一想,在现实生活中,当我们无法确定某个具体的东西的时候,往往把一类东西归于抽象类别。//工厂方法://比如你的工厂叫做“香烟工厂”,那么可以有“七匹狼工厂”“中华工厂”等,但是,这个工厂只生厂一种商品:香烟;//抽象工厂:无法描述它到底生产什么产品,它生产很多类型的产品(所以抽象工厂就会生成子工厂)。//你的工厂是综合型的,是生产“一系列”产品,而不是“一个”,比如:生产“香烟”,还有“啤酒”等。然后它也可以有派生出来的具体的工厂,但这些工厂都是生产这一系列产品,只是可能因为地域不一样,为了适应当地人口味,味道也不太一样。//工厂模式:理解成只生成一种产品的工厂。比如生产香烟的。//工厂方法:工厂的一种产品生产线 。比如键盘的生成过程。//别人会反驳:吃饱了没事干,一定要修改类名称呢?这个说不定。一般都不会去修改类名称。//其实工厂模式有很多变体,抓住精髓才是关键:只要是可以根据不同的参数生成不同的类实例,那么就符合工厂模式的设计思想。//工厂模式我想到的一个典型的应用就是:php可能要链接mysql,也可能要链接sqlserver,还有其他什么数据库。那么做一个抽象的数据库类,//这个类就是一个工厂类,专门负责产生不同的对象。//这样子做很方便扩展。我们在直接链接数据库的时候,不是使用代码new Mysql($host,$username,$password,$dbname)的形式//而可以动态生成一个连接数据库的实例。可以是mysql,也可以是连接oracle的。interface db { function connect();}interface Factory { function createDb();}class mysqldb implements db { public function connect() { echo '连上了mysql'; }}class sqlite implements db { public function connect() { echo '连上了sqllist'; }}class createMysql implements Factory { public function createDb(){ return new mysqldb(); }}class creareLite implements Factory { public function createDb(){ return new sqlite(); }}$fact = new createMysql();var_dump($fact->createDb()->connect());

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