malnew.cpp

#include <stdlib.h>
#include <iostream>

class MyClass
{
private:
    int *_number;

public:
    MyClass()
    {
        std::cout << "Allocate memory\n";
        _number = (int *)malloc(sizeof(int));
    }
    ~MyClass()
    {
        std::cout << "Delete memory\n";
        free(_number);
    }
    void setNumber(int number)
    {
        *_number = number;
        std::cout << "Number: " << _number << "\n";
    }
};

int main()
{
    /*
    // allocate memory using malloc
    // comment these lines out to run the example below
    MyClass *myClass = (MyClass *)malloc(sizeof(MyClass));
    myClass->setNumber(42); // EXC_BAD_ACCESS-> error coz constructor is not called and hence memory is not alocated for _number
    free(myClass);
    */
    // allocate memory using new
    MyClass *myClass = new MyClass();
    myClass->setNumber(42); // works as expected
    delete myClass;

    return 0;
}