45initializationlist.cpp

/*
INITIALISATION LIST :
this is a new way of writing a constructor with a new syntax
{{constructor name}} (arg1, arg2) : {{private variable 1}}(arg1), {{private variable 2}}(arg2)
{
    constructor body...
}
*/
#include <iostream>
using namespace std;

class Test
{
    int a, b; // this order is important to make the order of value initialising in constructor
public:
    Test(int x, int y) : a(x), b(y)
    {
        cout << "This is a constructor" << endl;
        cout << a << endl
             << b << endl;
    }
    /*
    OTHER POSSIBLE WAYS TO USE THIS SYNTAX OR POSSIBLE ACCURATE DECLARATION

    Test(int x, int y) : a(x), b(x + y){}
    Test(int x, int y) : a(x), b(a + y){}   Since a is already set
    Test(int x, int y) : a(x), b(2 * y){}

    Test(int x, int y) : b(y), a(b + x){} --> this is not valid and the value of a will not have b + x but instead a garbage
                                              value, this is due to the declaration or initialising order in the class
    Test(int x, int y) : b(x), a(y){}  --> Not valid

    Test(int x, int y) : a(x){
        b = y;
    }
    Test(int x, int y){     Basic syntax
        a = x;
        b = y;
    }
    */
};
int main()
{
    Test obj(2, 4);
    return 0;
}