How are the Constructor and Destructors called - c++

Question

#include<iostream>
class Example{
int i=0,j=0;
public:
Example(){
std::cout<<"Default Constructor is called "<<j++<<std::endl;
}
~Example(){
std::cout<<"Destructor is Called "<<i++<<std::endl;
}
void display(){
std::cout<<"Display method called "<<std::endl;
}
};
void function(){
Example e;
e.display();
}
int main(){
function();
Example e1;
}
I'm trying to see how the constructor and destructor are called for two objects of the same class
The output I'm getting is
Default Constructor is called 0
Display method is called
Destructor is called 0
Default Constructor is called 0
Destructor is called 0
Why is my i and j variable not getting incremented

Answer 1

Your i and j variables are incremented, but the results are not printed.
You used postfix increment operator, so it is evaluated to the value before incrementing.
As you say, there are two objects, and they have independend member variables i and j because they are not static.

Answer 2

Since both the objects are independent of each other so incremented values will not affect another object. They are incrementing , if you want to see the incremented value then you can try pre-increment by using ++i or ++j instead of i++ or j++.
To know more you comment.

Answer 3

You have 2 different objects of class Example namely e and e1. Where e belongs to your defined function function, and e1 belongs to the main function.
So when you execute your program, object e only gets called once and the values of i and j get incremented for that object. But then you use another object e1, for which their values different than previously called object e. That's why values of i and j are different for different objects. Every time you create a new object, they get initialized to 0 for that object.
Now, what you have to do to make these values same for all objects is to make those variables static. Static will make variables accessible to all objects you create of same class with unchanged value and they don't get initialize every time you create a new object.
Here is how you can do it:
static int i,j;
But make sure you don't initialize static variables inside class. Otherwise program will throw an error. So, to initialize your static variables to 0, access them outside of class and set them to whatever value you wish to initialize them with. Like following:
int Example::i = 0;
int Example::j = 0;
That's it. Now you can achieve what you were looking for.
So now your code must look something like this:
class Example{
static int i,j;
public:
Example(){
std::cout<<"Default Constructor is called "<<j++<<std::endl;
}
~Example(){
std::cout<<"Destructor is Called "<<i++<<std::endl;
}
void display(){
std::cout<<"Display method called "<<std::endl;
}
};
int Example::i = 0;
int Example::j = 0;
void function(){
Example e;
e.display();
}
int main(){
function();
Example e1;
}

Answer 4

Change has been made. Please run this again
#include<iostream>
class Example{
static int i,j; //Changed
public:
Example(){
std::cout<<"Default Constructor is called "<<j++<<std::endl;
}
~Example(){
std::cout<<"Destructor is Called "<<i++<<std::endl;
}
void display(){
std::cout<<"Display method called "<<std::endl;
}
};
int Example::i = 0; //initializing i and j like this outside the class
int Example::j = 0; //Added
void function(){
Example e;
e.display();
}
int main(){
function();
Example e1;
}