Question

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Is it ok to cast a STL container with Base type to Derived type?

This should be a quick question… If I have a container, say an STL list, of a base class, is it possible to casts the entire container to a type of subclass? E.g.

[A inherits from base class B]

list<B*> list1;
list1.push_back(new A());

list<A*> list2 = list1;

The compiler is complaining: “conversion from std::vector<B*, std:allocator<B*> >' to non-scalar type 'std::vector<Bar*, ...>' requested.“

Is this possible, or am I’m just screwing it up?

Answer 1

No. std::list<T> and std::list<U> are completely different, incompatible types, if std::is_same<T,U>::value is false, i.e if the type arguments T and U aren’t same.

Use std::transform and do appropriate casting in the callback.