Trying to push back structs/classes with std::variant

[oblique narwhal]

Firstly, not sure why the below code isn't working:

[frosty whale]

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[oblique narwhal]

;compile -std=c++23

#include <iostream>
#include <vector>
#include <variant>

struct Main {
  int a;
};

struct Bingo : Main {
  int b;
};

using Things = std::variant<Bingo>;

int main() {
  std::vector<Things> children;
  Bingo bingo;
  bingo.a = 5;
  bingo.b = 8;
  children.push_back(bingo);
  std::cout << children[0].a << "\n";
  std::cout << children[0].b << "\n";
}

[novel patio]

Compiler Output

<source>: In function 'int main()':
<source>:21:28: error: '__gnu_cxx::__alloc_traits<std::allocator<std::variant<Bingo> >, std::variant<Bingo> >::value_type' {aka 'class std::variant<Bingo>'} has no member named 'a'
   21 |   std::cout << children[0].a << "\n";
      |                            ^
<source>:22:28: error: '__gnu_cxx::__alloc_traits<std::allocator<std::variant<Bingo> >, std::variant<Bingo> >::value_type' {aka 'class std::variant<Bingo>'} has no member named 'b'
   22 |   std::cout << children[0].b << "\n";
      |                            ^
Build failed

kojobailey | c++ | x86-64 gcc 13.2 | godbolt.org

[oblique narwhal]

(There's only one struct in the variant rn bc I haven't added more yet)

this is simply a test compilation

[rapid jungle]

You need to use std::get to get the Bingo type from the variant

#include <iostream>
#include <variant>
#include <vector>

struct Main {
  int a;
};

struct Bingo : Main {
  int b;
};

using Things = std::variant<Bingo>;

int main() {
  std::vector<Things> children;
  Bingo bingo;
  bingo.a = 5;
  bingo.b = 8;
  children.push_back(bingo);
  std::cout << std::get<Bingo>(children[0]).a << "\n";
  std::cout << std::get<Bingo>(children[0]).b << "\n";
}

[oblique narwhal]

aha

;compile -std=c++23

#include <iostream>
#include <vector>
#include <variant>

struct Main {
  int a;
};

struct Bingo : Main {
  int b;
};

using Things = std::variant<Bingo>;

int main() {
  std::vector<Things> children;
  Bingo bingo;
  bingo.a = 5;
  bingo.b = 8;
  children.push_back(bingo);
  std::cout << std::get<Bingo>(children[0]).a << "\n";
  std::cout << std::get<Bingo>(children[0]).b << "\n";
}

[novel patio]

Program Output

5
8

kojobailey | 96ms | c++ | x86-64 gcc 13.2 | godbolt.org

[oblique narwhal]

thank you