C / C++ / MFC

pointer[0] = new Base;
etc...

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

<br />
<br />
class Base<br />
{<br />
public:<br />
int m_iInt;<br />
<br />
public:<br />
int virtual GetInt() {return m_iInt);<br />
CString virtual GetClassInfo() {return CString("Base")};<br />
int NonVirtualGetInt(){return m_iInt);<br />
}<br />
<br />
class Derive1 : Base<br />
{<br />
public: <br />
int m_iAnotherInt;<br />
<br />
public:<br />
int virtual GetInt() {return m_iAnotherInt);<br />
CString virtual GetClassInfo() {return CString("Derive1")};<br />
int NonVirtualGetInt(){return m_iAnotherInt);<br />
}<br />
<br />
class Derive2 : Base<br />
{<br />
<br />
public:<br />
int virtual GetInt() {return 2 * m_iInt);<br />
CString virtual GetClassInfo() {return CString("Derive1")};<br />
int NonVirtualGetInt(){return 2 * m_iInt);<br />
}<br />
<br />
int main()<br />
{<br />
Base *pointer[3];<br />
<br />
pointer[0] = new Base;<br />
pointer[1] = new Derive1;<br />
pointer[2] = new Derive2;<br />
<br />
pointer[0]->m_iInt = 1  // access Base.m_iInt<br />
pointer[1]->m_iInt = 10  // access Base.m_iInt although p1 is a Derive1<br />
(CDerive1*)pointer[1]->m_iAnotherInt = 15  // access Derive1.m_iAnotherInt<br />
(CDerive2*)pointer[2]->m_iInt = 100<br />
(CDerive2*)pointer[2]->m_iAnotherInt = 150 // won't work, Derive2 has not m_iAnotherInt<br />
<br />
for (i=0; i<3; i++) <br />
   cout << pointer[i]->GetInt()  // will write 1 (Base.GetInt(), 15 (Derive1.GetInt), 200 (Derive2.GetInt as GetInt is virtual<br />
<br />
for (i=0; i<3; i++)<br />
   cout << pointer[i]->m_iInt // 1, 10, 100, all classe contain m_iInt, but C++ think it's all Base.m_iInt<br />
<br />
for (i=0; i<3; i++)<br />
   cout << pointer[i]->m_iAnotherInt // won't work, m_iAnotherInt not member of Base, and C++ thinks all pointers are Base*<br />
<br />
for (i=0; i<3; i++)<br />
   cout << pointer[i]->NonVirtualGetInt() // returns 1, 10, 100 as Base.NonVirtualInt() is called in all three cases<br />
<br />
for (i=0; i<3; i++) {<br />
   CString cs=pointer[i]->GetClassInfo()<br />
   if (cs == "Base") pointer[i]->NonVirtualGetInt() // Base.NonVirtualGetInt()<br />
   if (cs == "Derive1") (Derive1*)pointer[i]->NonVirtualGetInt() // Derive1.NonVirtualGetInt()<br />
   if (cs == "Derive2") (Derive2*)pointer[i]->NonVirtualGetInt() // Derive2.NonVirutalGetInt()<br />
}<br />