add pointer

add smart pointer

CPlusPlus/Pointer/main.cpp

@@ -0,0 +1,69 @@
+#include <iostream>
+#include <memory> // smart pointer header
+
+#include "functions.h"
+
+using namespace std;
+
+int main()
+{
+	// general
+	int* pNumber = nullptr;
+	pNumber = new int(0);
+
+	cout << "pNumber: " << pNumber << endl;
+	cout << "*pNumber: " << *pNumber << endl;
+	cout << "size of pointer: " << sizeof(pNumber) << endl;
+	cout << "size of *pointer: " << sizeof(*pNumber) << endl;
+
+	*pNumber = 567;
+
+	//pNumber = new int(0); // BAD BAD - Memory Leak, because we overriding an existing pointer address with a new one
+
+	// here are 100s line of code OR at different position
+
+	if (pNumber != nullptr)
+	{
+		delete pNumber;
+		pNumber = nullptr;
+	}
+
+	// pointer as references
+	int number = 10;
+	changeInteger(number);
+	changeIntegerPerPointer(&number);
+	changeIntegerPerPointer(pNumber);
+	changeIntegerPerReference(number);
+	//changeIntegerPerReference(10); // doesn't work, because you need an existing & initialized variable for a reference
+
+	// smart pointer
+	// unique_ptr - only one owner exist for the object
+	// shared_ptr - can have multiple owners
+	// weak_ptr - is a loose connection to a shared_ptr
+
+	unique_ptr<int> pNumber2 = make_unique<int>(10);
+	*pNumber2 = 100;
+	//unique_ptr<int> pNumber3 = pNumber2; // compiler error - you can't create a copy of an unique pointer
+	unique_ptr<int> pNumber4 = make_unique<int>(*pNumber2);
+
+	shared_ptr<int> pNumber5 = make_shared<int>(10);
+	shared_ptr<int> pNumber6 = pNumber5;
+	*pNumber6 = 100;
+
+	pNumber5.reset();
+
+	weak_ptr<int> pNumber7 = pNumber6;
+	//*pNumber7 = 1000; // compiler error, because a weak pointer has no direct access to the shared pointer, you have to create a shared pointer object
+
+	if (!pNumber7.expired())
+	{
+		shared_ptr<int> pTmpSharedPointer = pNumber7.lock();
+		*pTmpSharedPointer = 10000;
+	}
+
+	pNumber6.reset();
+	shared_ptr<int> pTmpSharedPointer2 = pNumber7.lock();
+	if (pTmpSharedPointer2 != nullptr) *pTmpSharedPointer2 = 10; // smart pointer are no guarantee for a valid object behind the pointer
+
+	return 0;
+}