Not able to access members of a Union

Question

I haee this small piece of code in which I'm trying to create a struct Employee. The employee can be either a manager or worker. I'm having trouble accessing members of the unions. Here's my code

#include <iostream>
#include <string>
using namespace std;

struct Employee {
 int id;
 union Person {
  struct Manager {
   int level;
  } manager;
  struct Worker {
   string department;
  } worker;
 } company[3];
};


int main() {
 Employee one;
 one.id = 101;
 one.company[0].manager.level = 3;

 Employee two;
 two.id = 102;
 two.company[1].worker.department = "Sales";

 Employee three;
 three.id = 103;
 three.company[2].worker.department = "Marketing";
}

The error I get is

arraOfUnions.cc:13:5: error: member 'Employee::Person::Worker Employee::Person::worker' with constructor not allowed in union
arraOfUnions.cc:13:5: error: member 'Employee::Person::Worker Employee::Person::worker' with destructor not allowed in union
arraOfUnions.cc:13:5: error: member 'Employee::Person::Worker Employee::Person::worker' with copy assignment operator not allowed in union
arraOfUnions.cc:13:5: note: unrestricted unions only available with -std=c++0x or -std=gnu++0x

I'm not sure what I'm doing wrong. Please help Thanks SO

unrestricted union in c++11 would require a constructor for `Person`. — Jarod42, Mar 07 '16 at 23:05
`union` is the wrong approach for whatever you are trying to do — M.M, Mar 07 '16 at 23:37
Possible duplicate of [Why compiler doesn't allow std::string inside union?](http://stackoverflow.com/questions/3521914/why-compiler-doesnt-allow-stdstring-inside-union) — user4581301, Mar 07 '16 at 23:42
@Q_A, POD stands for Plain-Old Data. However, to expand upon what M.M said, you would probably be better off using inheritance to implement this. Specifically, `Manager` and `Worker` could both be sub-classes of `Employee`. — Joe F, Mar 07 '16 at 23:52

score 2 · Answer 1 · edited May 23 '17 at 11:45

2

You cannot have a non-POD object in your union, but you can have a pointer to a non PDO object (therefore string* is valid).

What are POD types in C++?

Pehaps a const char* is enough, if all you need is access to those string literals "Sales" & "Marketing"-

edited May 23 '17 at 11:45

Community

1
1

answered Mar 07 '16 at 23:10

Jts

3,447
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score 0 · Answer 2 · answered Mar 08 '16 at 16:56

BTW - you data model is completely wrong. You should not be using a union you need to use a class hierarchy.

You need a base class Employee, and a derived class Manager.

struct Employee {
   int id;
  string department;
};

struct Manager : public Employee
{
  int level;
}

and dont use struct use class

and have better naming for members. like m_company or company_

and dont do using namespace std, say std::string etc

class Employee {
   int _id;
  std::string _department;
};

class Manager : public Employee
{
  int _level;
}

Not able to access members of a Union

2 Answers2