add example for "default constructor, copy constructor, destructor, if you need one you'll need all"

add smart pointer
add pointer pointer

CPlusPlus/Pointer/main.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <memory> // smart pointer header
 
 using namespace std;
 
@@ -7,6 +8,9 @@ void changeIntegerPerPointer(int* pN);
 int changeIntegerPerReturn(int n);
 void changeIntegerPerReference(int& n);
 
+bool createInteger(int* pN);
+bool createIntegerWithPointerPointer(int** ppN);
+
 int main()
 {
 	// general
@@ -18,7 +22,7 @@ int main()
 
 	*pNumber = 567;
 
-	//pNumber = new int(0); // BAD BAD - Memory Leak, because we override an existing pointer address with a new one without saving the old one
+	// pNumber = new int(0); // BAD BAD - Memory Leak, because we override an existing pointer address with a new one without saving the old one
 	
 	// here are 100s of lines of code
 	
@@ -29,11 +33,57 @@ int main()
 	}
 
 	// pointer as references
-	int number = 0;
-	changeInteger(number);
-	changeIntegerPerPointer(&number);
-	changeIntegerPerPointer(pNumber);
-	changeIntegerPerReference(number);
+	//int number = 0;
+	//changeInteger(number);
+	//changeIntegerPerPointer(&number);
+	//changeIntegerPerPointer(pNumber);
+	//changeIntegerPerReference(number);
+
+	// smart pointer
+	// unique_ptr -> only one owner exist for the object
+	// shared_ptr -> can have multiple owners
+	// weak_ptr -> is loose connection to a shared_ptr
+
+	unique_ptr<int> number = make_unique<int>(10);
+	*number = 100;
+	//unique_ptr<int> number2 = number; // compiler error - you can create a copy of an unique pointer
+	unique_ptr<int> number2 = make_unique<int>(*number);
+
+	shared_ptr<int> number3 = make_shared<int>(20);
+	shared_ptr<int> number4 = number3;
+	*number3 = 200;
+	*number4 = 2000;
+
+	number3.reset();
+
+	weak_ptr<int> weakNumber = number4;
+	//*weakNumber = 20000; // compiler error, weak pointer have no direct access to a shared pointer, you have to create one
+
+	if (!weakNumber.expired())
+	{
+		shared_ptr<int> tmpSharedNumber = weakNumber.lock();
+		*tmpSharedNumber = 20000;
+	}
+
+	number4.reset();
+	shared_ptr<int> tmpSharedNumber = weakNumber.lock();
+
+	// pointer-pointer
+	if (createInteger(pNumber))
+	{
+		cout << "Create integer was succesful" << endl;
+	}
+
+	if (createIntegerWithPointerPointer(&pNumber))
+	{
+		cout << "Create integer was succesful" << endl;
+	}
+
+	if (pNumber != nullptr)
+	{
+		delete pNumber;
+		pNumber = nullptr;
+	}
 
 	return 0;
 }
@@ -56,3 +106,17 @@ void changeIntegerPerReference(int& n)
 {
 	n = 300;
 }
+
+bool createInteger(int* pN)
+{
+	pN = new int(0); // CAUTION - creates a MEMORY LEAK
+
+	return false;
+}
+
+bool createIntegerWithPointerPointer(int** ppN)
+{
+	*ppN = new int(0);
+
+	return true;
+}