C / C++ / MFC

int foo1() const

template   <typename T>
class propertyQ 
{
public:
     static void QMethod1(T &objT)
	 {
		 objT.operate1();
	 }

	 static void QMethod2(T &objT)
	 {
		 objT.operate2();
	 }
};

class superTypeA
{
protected:
	int m_iContext;
public:

	superTypeA()
		: m_iContext(0)
	{
	}
	void operate1()
	{
		m_iContext = 1;		
	}

	void operate2()
	{
		m_iContext = 2;		
	}
};

class subTypeA : public superTypeA
{
public:
	void operate2()
	{
		m_iContext = 21;	
	}
};

class subTypeB : private superTypeA
{
public:
	void operate2()
	{
		m_iContext = 21;	
	}
};

int main()
{
	subTypeA objA;
	subTypeB objB;
	propertyQ <subTypeA>::QMethod1(objA);
	propertyQ <subTypeB>::QMethod1(objB); // error, cannot be subtitutable
     return 0;
}

George_George wrote:

Now I understand this principle to be, if we have some methods in base class, then we also need to implement the methods in derived class. My understanding correct?

George_George wrote:

But the description is not common senses.

Rajkumar R wrote:

structural subtype is that eventhough u didnot inherit from base class, class superTypeA, if u r implementing all the functions in every class you are able to apply the property, class propertyQ.

George_George wrote:

What means "if u r implementing all the functions in every class" and "you are able to apply the property, class propertyQ"? What do you mean all the functions and every class?

struct subTypeA
{
	subTypeA()
		: m_iContext(0)
	{
	}
	void operate1()
	{
		m_iContext = 1;		
	}

	void operate2()
	{
		m_iContext = 2;		
	}
	private:
	int m_iContext;
};

struct subTypeB
{
	subTypeB()
		: m_iContext(0)
	{
	}
	void operate1()
	{
		m_iContext = 1;		
	}

	void operate2()
	{
		m_iContext = 2;		
	}
private:
	int m_iContext;
};

George_George wrote:

My stupid before.

void propertyQ(superTypeA *obj)
{
	obj->operate1();
}

subTypeA objA;
subTypeB objB;

propertyQ(&objA);
propertyQ(&objB); // error C2243: 'type cast' : conversion from 'subTypeB 
               *__w64 ' to 'superTypeA *' exists, but is inaccessible

li zhiyuan wrote:

thanks for your reminder, i didn't find, can you send me again.