「软件设计模式」工厂方法模式 vs 抽象工厂模式

前言

在软件工程领域，设计模式是解决常见问题的经典方案。本文将深入探讨两种创建型模式：工厂方法模式和抽象工厂模式，通过理论解析与实战代码示例，帮助开发者掌握这两种模式的精髓。

一、工厂方法模式（Factory Method Pattern）

1.1 模式思想

工厂方法模式的核心在于将对象的创建延迟到子类，通过定义创建对象的接口，让子类决定实例化哪个类。这种模式完美体现了依赖倒置原则。

1.2 模式结构

Product：抽象产品接口
ConcreteProduct：具体产品实现
Creator：抽象创建者
ConcreteCreator：具体创建者

1.3 代码示例

#include <iostream>
#include <string>class Shape {
public:virtual void draw() = 0;
};class Circle : public Shape {void draw() {std::cout << "Circle::draw()" << std::endl;}
};class Rectangle : public Shape {void draw() {std::cout << "Rectangle::draw()" << std::endl;}
};class Square : public Shape {void draw() {std::cout << "Square::draw()" << std::endl;}
};class ShapeFactory {
public:Shape* getShape(const std::string& shapeType) {if (shapeType.empty()) {return nullptr;}if (shapeType == "CIRCLE") {return new Circle();} else if (shapeType == "RECTANGLE") {return new Rectangle();} else if (shapeType == "SQUARE") {return new Square();}return nullptr;}
};

#include "factory_mode.h"int main(int argc, char const* argv[]) {ShapeFactory* shapeFactory = new ShapeFactory();Shape* shape1 = shapeFactory->getShape("CIRCLE");shape1->draw();Shape* shape2 = shapeFactory->getShape("RECTANGLE");shape2->draw();Shape* shape3 = shapeFactory->getShape("SQUARE");shape3->draw();delete shapeFactory;return 0;
}

1.4 运行结果

1.5 适用场景

需要灵活扩展产品类型
创建过程需要封装处理逻辑
需要解耦客户端与具体产品类

二、抽象工厂模式（Abstract Factory Pattern）

2.1 模式思想

抽象工厂模式通过创建相关对象族来提升系统的扩展性，强调产品系列的概念。它比工厂方法模式更高层次的抽象。

2.2 模式结构

AbstractFactory：抽象工厂接口
ConcreteFactory：具体工厂实现
AbstractProduct：抽象产品接口
ConcreteProduct：具体产品实现

2.3 代码示例

产品定义：

#include <iostream>
#include <string>
// 
class Color {
public:virtual void fill() = 0;
};class Red : public Color {
public:void fill() {std::cout << "Red::fill()" << std::endl;}
};class Green : public Color {
public:void fill() {std::cout << "Green::fill()" << std::endl;}
};class Blue : public Color {
public:void fill() {std::cout << "Blue::fill()" << std::endl;}
};
// 形状产品
class Shape {
public:virtual void draw() = 0;
};class Circle : public Shape {void draw() {std::cout << "Circle::draw()" << std::endl;}
};class Rectangle : public Shape {void draw() {std::cout << "Rectangle::draw()" << std::endl;}
};class Square : public Shape {void draw() {std::cout << "Square::draw()" << std::endl;}
};

抽象工厂

#include "color.h"
#include "shape.h"
// 抽象工厂
class AbstractFactory {
public:virtual Shape* getShape(const std::string& shapeType) = 0;virtual Color* getColor(const std::string& colorType) = 0;
};

实体工厂

#include "abstract_factory.h"
// 实体工厂类// 形状工厂
class ShapeFactory : public AbstractFactory {
public:Shape* getShape(const std::string& shapeType) {if (shapeType.empty()) {return nullptr;}if (shapeType == "CIRCLE") {return new Circle();} else if (shapeType == "RECTANGLE") {return new Rectangle();} else if (shapeType == "SQUARE") {return new Square();}return nullptr;}Color* getColor(const std::string& colorType) {return nullptr;}
};// 颜色工厂
class ColorFactory : public AbstractFactory {
public:Color* getColor(const std::string& colorType) {if (colorType.empty()) {return nullptr;}if (colorType == "RED") {return new Red();} else if (colorType == "GREEN") {return new Green();} else if (colorType == "BLUE") {return new Blue();}return nullptr;}Shape* getShape(const std::string& shapeType) {return nullptr;}
};

生产商：

#include "factory.h"class FactoryProducer {
public:static AbstractFactory* getFactory(const std::string& choice) {if (choice == "SHAPE") {return new ShapeFactory();} else if (choice == "COLOR") {return new ColorFactory();}return nullptr;}
};

main：

#include "producer.h"// 抽象工厂 demo
int main(int argc, char const* argv[]) {AbstractFactory* shapeFactory = FactoryProducer::getFactory("SHAPE");Shape* shape1 = shapeFactory->getShape("CIRCLE");shape1->draw();Shape* shape2 = shapeFactory->getShape("RECTANGLE");shape2->draw();Shape* shape3 = shapeFactory->getShape("SQUARE");shape3->draw();AbstractFactory* colorFactory = FactoryProducer::getFactory("COLOR");Color* color1 = colorFactory->getColor("RED");color1->fill();Color* color2 = colorFactory->getColor("GREEN");color2->fill();Color* color3 = colorFactory->getColor("BLUE");color3->fill();delete shapeFactory;delete colorFactory;return 0;
}

2.4 运行结果

2.5 适用场景

需要创建多个相关对象组成的系列
系统需要支持不同产品族的切换
产品对象之间存在约束关系

三、核心差异对比

维度	工厂方法模式	抽象工厂模式
抽象层次	单个产品创建	产品族创建
扩展方向	垂直扩展（新增产品类型）	水平扩展（新增产品族）
实现方式	继承	组合
系统复杂度	简单	复杂
典型应用场景	日志记录器、支付方式	跨平台UI组件、数据库访问