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;

}