Compile Error with std::deque::erase with const members of the class

Question

I get an compile error here and I have no idea whats wrong with the code. I am using g++ 4.9.2.

#include<iostream>
#include<deque>

using std::string;
using std::deque;

class Dummy {
public:
    virtual ~Dummy(){};
    Dummy():ID_("00") {};
private:

    const string ID_;
};

int main(){
    {
    deque <Dummy> waiter;
    waiter.push_back(Dummy());
    waiter.erase( waiter.begin() );
    }
    return 0;
}

Edit: I know that removing the const removes the compilation error, but I have no idea why. Anyway, I need this const.

Answer 1

std::deque::erase expects the type of element should be MoveAssignable:

Type requirements

T must meet the requirements of MoveAssignable.

And class Dummy has a const member const string ID_;, which make it not assignable by default assignment operator.

You might make ID_ a non-const member, or provide your own assignment operator to make it assignable. e.g.

Dummy& operator=(const Dummy&) { /* do nothing */ }

LIVE

Answer 2

you should remove the const prefix, so that the string can be changed:

string ID_;

or else change it to a static variable and initialize it like this:

class Dummy {
public:
    virtual ~Dummy(){};
    Dummy() {};
private:

    static const string ID_;
};

const string Dummy::ID_ = "00";

you can find more information here about const string initialisation.