Can anyone explain me how above code works and using which concept?

Question

 #include<iostream>

  using namespace std;

    class A
   {

   public:
   A(int x)
   {
   a=x;
    }

   int a;
    };

  void fun(A temp)
  {
  cout<<temp.a<<endl;
  }

  int main()
  {
  fun(1);
   }

Here we are passing primitive values to fun method and catching using object of class A. can anyone explain me how above code works and using which concept?

these are very basics concepts and should be covered in the first chapters of any good [book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) — 463035818_is_not_an_ai, May 14 '17 at 10:21

score 0 · Answer 1 · answered May 14 '17 at 10:27

0

Class A has a constructor which receives an integer as a parameter.

Therefore, the integer parameter passed to fun is automatically casted to A.

In this automatic cast process, an A object (called temp) is created, and it's field 'a' is initialized with 1.

answered May 14 '17 at 10:27

ibezito

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Thanks for explaining, but one more doubt what would happen during cast process if we have more than one data members in A class and we are just passing 1 value? – Nirav May 14 '17 at 10:34
the automatic casting will work according to how you defined you constructor. – ibezito May 14 '17 at 10:40

score 0 · Accepted Answer · answered May 14 '17 at 10:30

I commented the code for you and made it a bit more clear to read. Read the comments from (1) -> (5).

#include <iostream>

using namespace std;

class A {

public:
    A(int x) // (3): gets called by f to initialize an object of class A with x=1
    {
        a = x;
    }

    int a;
};

void fun(A temp) // (2): Assumes 1 is a type class A. But it hasn't yet been initialized. So it calls Constructor. (tmp = new A(1))
{
    // (4): Now temp is an object of class A
    cout << temp.a << endl; // Prints temp.a
    // (5): temp object is getting destroyed.
}

int main()
{
    fun(1); // (1): Calls fun() with argument of 1
}

Can anyone explain me how above code works and using which concept?

2 Answers2