Как глубоко скопировать вариант указателей в C++? ⇐ C++

[Гость]

У меня есть

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std::variant

whose alternatives are all pointers.

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class a {
public:
int* placeholder;
a(a& _copy) { /* Does a deep copy */ }
}

class b {
// For demonstrational purposes, identical to a.
}

int main() {
std::vector instances = // initialise vector, guaranteed no nullptrs.
}

Now, for instance, if I want to push a deep copy of the first element to the back, I cannot simply do

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instances.push_back(instances[0])

, because that does a shallow copy of the

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vector

.
Of course, the obvious solution would be to check for all alternatives, then

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get_if

, create a copy, and return the copy. However, I think there has to be a better way. How should something as such be done?
I am also open to solutions that do not use variants.


Источник: https://stackoverflow.com/questions/781 ... nters-in-c