python设计模式 之 简单工厂模式

简单工厂模式属于类的创建型模式，适合用来对大量具有共同接口的类进行实例化，它能够推迟到执行的时候才动态决定要创建哪个类的实例。而不是在编译时就必须知道要实例化哪个类。

python:

#!/usr/bin/env python
# -*- coding: utf-8 -*-

class Circle(object):
	def draw(self):
		print 'draw circle'

class Rectangle(object):
	def draw(self):
		print 'draw Rectangle'

class ShapeFactory(object):
	def create(self, shape):
		if shape == 'Circle':
			return Circle()
		elif shape == 'Rectangle':
			return Rectangle()
		else:
			return None

fac = ShapeFactory()
obj = fac.create('Circle')
obj.draw()

c++:

#include <iostream>
#include <string.h>
using namespace std;

class Shape
{
public:
	virtual void draw(){}
};

class Circle : public Shape
{
public:
	void draw()
	{
		cout << "draw circle" << endl;
	}
};

class Rectangle : public Shape
{
public:
	void draw()
	{
		cout << "draw Rectangle" << endl;
	}
};

class ShapeFactory
{
public:
	static Shape* create(const char *opt)
	{
		if (opt == NULL)
			return NULL;

		if (!strcmp(opt, "Circle"))
			return new Circle();
		else if (!strcmp(opt, "Rectangle"))
			return new Rectangle();
		else
			return NULL;
	}
};

int main()
{
	Shape *obj = ShapeFactory::create("Rectangle");

	if (obj)
		obj->draw();

	return 0;
}