Traits技术

• traits=特性

提取不同类的共性，统一处理

依靠显示模板特殊化，把代码中因不同类型发生变化的片段提取出，用统一的接口来包装

接口可以为c++类所能包含的任何东西

客户通过traits模板类公开的接口来间接访问

• 代码示例

#include <iostream>

using namespace std;

class CIntArray
{
public:
	CIntArray();
	~CIntArray(){}

	int GetSum(int times);

private:
	int m_a[10];

};

CIntArray::CIntArray()
{
	for (int i = 0; i < 10; i++) {
		m_a[i] = i + 1;
	}
}

int CIntArray::GetSum(int times)
{
	int sum = 0;
	for (int i = 0; i < 10; i++) {
		sum += m_a[i];
	}
	return sum * times;
}


class CFloatArray
{
public:
	CFloatArray();
	~CFloatArray(){}

	float GetSum(float times);

private:
	float m_a[10];

};

CFloatArray::CFloatArray()
{
	for (int i = 0; i < 10; i++) {
		m_a[i] = i + 1;
	}
}

float CFloatArray::GetSum(float times)
{
	float sum = 0.0;
	for (int i = 0; i < 10; i++) {
		sum += m_a[i];
	}
	return sum * times;
}

// traist模板类
template<class T>
class NumTraits {};

//模板类特殊化
template<>
class NumTraits<CIntArray>
{
public:
	typedef int resultType;
	typedef int inputPara;
};

//模板类特殊化
template<>
class NumTraits<CFloatArray>
{
public:
	typedef float resultType;
	typedef float inputPara;
};

//对外接口
template<class T>
class CApply
{
public:
	typedef typename NumTraits<T>::resultType result;
	typedef typename NumTraits<T>::inputPara input;
	result GetSum(T& obj, input in)
	{
		return obj.GetSum(in);
	}
};

int main()
{
	CIntArray cInt;
	CApply<CIntArray> ci;
	std::cout << ci.GetSum(cInt, 3) << std::endl;

	CFloatArray cFloat;
	CApply<CFloatArray> cf;
	std::cout << cf.GetSum(cFloat, 5.5) << std::endl;
	
	return 0;


}