对象行为模式——策略模式（Strategy）

翻译于 2012-05-30 20:38:02 发布 · 277 阅读

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本文通过C++代码演示了策略模式的基本实现。策略模式定义了一系列的算法，并将每一个算法封装起来，使它们可以相互替换。该文展示了如何使用策略模式在运行时选择合适的算法。

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#include <iostream>
#include <list>
#include <algorithm>
using namespace std;

class Strategy
{
public:
	virtual void AlgorithmInterface() = 0;
};
class Context
{
public:
	Context(Strategy *pStrategy=NULL):m_pStrategy(pStrategy) {}
	void ContextInterface()
	{
		if (m_pStrategy)
		{
			m_pStrategy->AlgorithmInterface();
		}
	}
	void setStrategy(Strategy* s){m_pStrategy=s;}
private:
	Strategy* m_pStrategy;
};
class ConcreateStrategyA: public Strategy
{
public:
	virtual void AlgorithmInterface()
	{
		cout << "AlgorithmInterface Implemented by ConcreateStrategyA\n";
	}
};
class ConcreateStrategyB: public Strategy
{
public:
	virtual void AlgorithmInterface()
	{
		cout << "AlgorithmInterface Implemented by ConcreateStrategyB\n";
	}
};
int main()
{
	Strategy* pStrategyA = new ConcreateStrategyA();
	Context*  pContext  = new Context(pStrategyA);
	pContext->ContextInterface();
	Strategy* pStrategyB = new ConcreateStrategyB();
	pContext->setStrategy(pStrategyB);
	pContext->ContextInterface();
	return 0;
}