创建型设计模式-工厂方法 Factory Method

简介

工厂方法中，每一个具体工厂类都对应创建一个具体产品类，所有具体工厂类都实现抽象工厂，所有具体产品类都实现抽象产品。

抽象工厂定义了创建抽象产品的方法签名，具体工厂类各自实现各自逻辑，来创建具体的产品。

角色

• 抽象工厂 Abstract Factory

  定义创建产品的方法签名，即Factory Method

• 抽象产品 Abstract Product

  定义产品的基本属性

• 具体工厂 Concrete Factory

  实现自抽象工厂，并实现 Factory Method，实现如何创建具体产品。

• 具体产品 Concrete Product

  实现具体产品基本属性

类图

如图所示，Dialog抽象工厂可以创建Button抽象产品，WindowsDialog和WebDialog都是具体工厂，负责创建WindownsButton和HTMLButton。

代码

abstract class Creator
{
    abstract public function factoryMethod(): Product;

    public function someOperation(): string
    {
        $product = $this->factoryMethod();
        $result = "Creator: The same creator's code has just worked with " . $product->operation();
        return $result;
    }
}

class ConcreteCreator1 extends Creator
{
    public function factoryMethod(): Product
    {
        return new ConcreteProduct1();
    }
}

class ConcreteCreator2 extends Creator
{
    public function factoryMethod(): Product
    {
        return new ConcreteProduct2();
    }
}

interface Product
{
    public function operation(): string;
}

class ConcreteProduct1 implements Product
{
    public function operation(): string
    {
        return "{Result of the ConcreteProduct1}";
    }
}

class ConcreteProduct2 implements Product
{
    public function operation(): string
    {
        return "{Result of the ConcreteProduct2}";
    }
}

function clientCode(Creator $creator)
{
    echo "Client: I'm not aware of the creator's class, but it still works.\n" . $creator->someOperation() . "\n";
}

echo "App: Launched with the ConcreteCreator1.\n";
clientCode(new ConcreteCreator1());

echo "App: Launched with the ConcreteCreator2.\n";
clientCode(new ConcreteCreator2());

output

App: Launched with the ConcreteCreator1.
Client: I'm not aware of the creator's class, but it still works.
Creator: The same creator's code has just worked with {Result of the ConcreteProduct1}
App: Launched with the ConcreteCreator2.
Client: I'm not aware of the creator's class, but it still works.
Creator: The same creator's code has just worked with {Result of the ConcreteProduct2}