CODEWITHSUNDEEP
c++oopinheritance
noobcoder
noobcoder

Reputation: 160

Could someone explain this inheritance code?

#include <iostream>
using namespace std;

struct A {
    A() { cout << "A "; } 
};

struct B: A {
    B() { cout << "B "; }  
};

struct C: A {
    C() { cout << "C "; } 
};

struct D: C, B {
    D() { cout << "D "; }    
};

int main(){
    D d;
}

The result is A C A B D. My understanding is that D inherits from C and B, and if an object "d" is created in D, then it also has the attributes from C and B. And since B and C both inherits from A, D should also inherit from A. Can someone explain the result please? My prediction is way off...

Upvotes: 1

Views: 66

Answers (2)

user1023602
user1023602

Reputation:

The base constructor(s) are called first, then the main constructor.

    D()
=>  C()    then  B()    then D
=>  A() C  then  A() B  then D
=>  A C    then  A B    then D
=>  A C A B D

Order of execution in constructor initialization list

Upvotes: 1

Andres
Andres

Reputation: 10725

Inheritance reflects an IS A relationship.

A D object is a C and a B. A C is in turn an A. Therefore, to create an instance of D, the runtime has to first create an A and then a C. That explains the first two characters of the output. Continue with this reasoning and you'll get the rest.

Upvotes: 0

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