I've tried to construct a tree structure using boost::variant and now I have some problems. I implemented a copy constructor in the class holden in boost::variant and call the copy constructor just like this code:
#include <iostream>
#include <boost/variant.hpp>
struct Hoge{
int i;
Hoge(int j) : i(j){};
Hoge(Hoge const& hoge) : i(hoge.i) {}
};
using var = boost::variant<int,Hoge>;
int main()
{
var hoge = Hoge(1);
var hogehoge = Hoge(hoge);
}
A compile failed because of no matching function for call to ‘Hoge::Hoge(var&)’.
How to fix this code? Should the copy constructor has an argument boost::variant? Or can I fix this code with an brilliant boost technique?
You're not copy constructing: that would be like saying:
var hogehoge = var(hoge); // elided assign of copy-ctor
Or indeed just
var hogehoge(hoge);
var hogehoge = hoge;
So, what you need is to SAY you want a Hoge
to copy,
var hogehoge = boost::get<Hoge>(hoge); // may throw if `hoge` holds int
So you copy-construct Hoge, which you then convert-construct to the variant type.
See it Live On Coliru
#include <boost/variant.hpp>
#include <iostream>
struct Hoge {
int i;
Hoge(int j) : i(j){};
Hoge(Hoge const& hoge) : i(hoge.i) {}
};
using var = boost::variant<int, Hoge>;
int main() {
var hoge = Hoge(1);
var hogehoge = boost::get<Hoge>(hoge);
}