add pure virtual

add interfaces like classes
add template example

CPlusPlus/intro/ClassA.cpp

@@ -2,6 +2,7 @@
 
 ClassA::ClassA() : _pNumber(new int(0))
 {
+	std::cout << "ClassA() called" << std::endl;
 }
 
 ClassA::ClassA(const ClassA& other)
@@ -15,9 +16,15 @@ ClassA::ClassA(const ClassA& other)
 
 ClassA::~ClassA()
 {
+	std::cout << "~ClassA() called" << std::endl;
 	if (_pNumber != nullptr)
 	{
 		delete _pNumber;
 		_pNumber = nullptr;
 	}
 }
+
+bool ClassA::Compare(IComparable* pOther)
+{
+	return false;
+}

CPlusPlus/intro/ClassA.h

@@ -1,6 +1,7 @@
 #pragma once
+#include "IComparable.h"
 
-class ClassA
+class ClassA : public IComparable
 {
 	// private
 
@@ -8,7 +9,10 @@ public:
 	// public
 	ClassA(); // default constructor
 	ClassA(const ClassA& other); // copy constructor
-	~ClassA(); // destructor
+	virtual ~ClassA(); // destructor
+
+	const int& GetNumber() const { return *_pNumber; } // implicit inline method
+	bool Compare(IComparable* pOther) override;
 
 protected:
 	// protected

CPlusPlus/intro/ClassB.cpp

@@ -0,0 +1,12 @@
+#include "ClassB.h"
+
+ClassB::ClassB()
+{
+	std::cout << "ClassB() called" << std::endl;
+	GetNumber();
+}
+
+ClassB::~ClassB()
+{
+	std::cout << "~ClassB() called" << std::endl;
+}

CPlusPlus/intro/ClassB.h

@@ -0,0 +1,10 @@
+#pragma once
+#include "ClassA.h"
+
+class ClassB : public ClassA
+{
+public:
+	ClassB();
+	~ClassB();
+};
+

CPlusPlus/intro/IComparable.h

@@ -0,0 +1,10 @@
+#pragma once
+#include <iostream>
+
+class IComparable
+{
+public:
+	IComparable() { std::cout << "IComparable() called" << std::endl; }
+	virtual ~IComparable() { std::cout << "~IComparable() called" << std::endl; }
+	virtual bool Compare(IComparable* pOther) = 0;
+};

CPlusPlus/intro/functions.h

@@ -9,4 +9,14 @@ void changeInt(int n);
 void changeIntPointer(int* pN);
 void changeIntReference(int& n);
 
+template<class T>
+void safeDelete(T*& pObj)
+{
+	if (pObj != nullptr)
+	{
+		delete pObj;
+		pObj = nullptr;
+	}
+}
+
 #endif // __FUNCTIONS_H__

CPlusPlus/intro/intro.vcxproj

@@ -128,12 +128,15 @@
   </ItemDefinitionGroup>
   <ItemGroup>
     <ClCompile Include="ClassA.cpp" />
+    <ClCompile Include="ClassB.cpp" />
     <ClCompile Include="functions.cpp" />
     <ClCompile Include="main.cpp" />
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="ClassA.h" />
+    <ClInclude Include="ClassB.h" />
     <ClInclude Include="functions.h" />
+    <ClInclude Include="IComparable.h" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">

CPlusPlus/intro/intro.vcxproj.filters

@@ -24,6 +24,9 @@
     <ClCompile Include="ClassA.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="ClassB.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="functions.h">
@@ -32,5 +35,11 @@
     <ClInclude Include="ClassA.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="ClassB.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="IComparable.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>

CPlusPlus/intro/main.cpp

@@ -3,6 +3,7 @@
 #include <memory>
 #include "functions.h"
 #include "ClassA.h"
+#include "ClassB.h"
 
 int number = 0;
 
@@ -115,8 +116,42 @@ int main()
 
 	//cout << "sn2 refs: " << sn2.use_count() << endl;
 
-	ClassA classA;
-	ClassA classA2 = classA;
+	//ClassA classA;
+	//ClassA classA2 = classA;
+	//ClassB classB;
+
+	//int number = classA.GetNumber();
+	//cout << number << endl;
+	//classB.GetNumber();
+
+	//IComparable* pComparable = nullptr;
+	//pComparable = new ClassB();
+	////ClassB* pClassB2 = (ClassB*)pComparable; // C-Cast, CAUTION: DANGER!!!
+	//ClassB* pClassB2 = dynamic_cast<ClassB*>(pComparable); // C++ polymorph cast
+	//float f = 1.0f;
+	//int i = static_cast<int>(f); // explicit c++ cast between two static data types
+	////int* pNonsense = reinterpret_cast<int*>(pComparable); // c++ cast like C-Cast
+	//const char csz[13] = "Hello World";
+	//char* sz = const_cast<char*>(csz);
+
+	// What's the difference?
+	//const int* cip;
+	//int const* icp;
+	//int* const ipc;
+	//const int* const cipc;
+	//int const* const icpc;
+	//const int const* const cicpc;
+
+	IComparable* pComparable = nullptr;
+	IComparable* pComparable2 = new ClassA();
+	pComparable = new ClassB();
+	(*pComparable).Compare(pComparable2);
+	pComparable->Compare(pComparable2); // identical to line above, but simpler
+	delete pComparable;
+	pComparable = nullptr;
+	//delete pComparable2;
+	//pComparable2 = nullptr;
+	safeDelete(pComparable2);
 
 	return 0;
 }