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