变量承接函数类型的方法

重点：

1.当两个类没有共同基类。

采用函数模板：类具有相同的函数

class FirstCmd 
{
public:
	FirstCmd()=default;
	~FirstCmd() = default;

	void TestCmd() { std::cout << 10 << std::endl;};
};


class SecondCmd
{
public:
	SecondCmd() = default;
	~SecondCmd() = default;

	void TestCmd() { std::cout << 20 << std::endl; };
};



template<class T>
void Get(T* a)
{
	a->TestCmd();
}

int main()
{
	int a = 3;
	int b = a * a * a-a;
	FirstCmd* first=new FirstCmd();
	SecondCmd* second =new SecondCmd();

	auto iter = dynamic_cast<FirstCmd*>(first);
	auto se = dynamic_cast<SecondCmd*>(second);
	if (iter == nullptr)
	{
		Get(se);
	}
	else
	{
		Get(iter);
	}
	return 0;
}

2.当两个类有共同基类。

采用向下转型方式

class BaseCmd
{
public:
	BaseCmd() = default;
	~BaseCmd() = default;

	virtual void TestCmd() = 0;
};



class FirstCmd:public BaseCmd
{
public:
	FirstCmd()=default;
	~FirstCmd() = default;

	virtual void TestCmd() { std::cout << 10 << std::endl;};
};


class SecondCmd :public BaseCmd
{
public:
	SecondCmd() = default;
	~SecondCmd() = default;

	virtual void TestCmd() { std::cout << 20 << std::endl; };
};

std::shared_ptr<BaseCmd> GetBaseCmd(bool check)
{
	if (check)
	{
		return std::make_shared<FirstCmd>();
	}
	else
	{
		return std::make_shared<SecondCmd>();
	}
}

int main()
{
	bool check{ false };

	auto base =GetBaseCmd(check);
	base->TestCmd();
	std::shared_ptr<BaseCmd> baseCmd = std::dynamic_pointer_cast<FirstCmd>(base);
	if (!baseCmd)
	{
		baseCmd=  std::dynamic_pointer_cast<SecondCmd>(base);
	}
	
	if (baseCmd)
	{
		baseCmd->TestCmd();
	}
	return 0;
}