function template
<memory>
std::dynamic_pointer_cast
template <class T, class U> shared_ptr<T> dynamic_pointer_cast (const shared_ptr<U>& sp) noexcept;
Dynamic cast of shared_ptr
Returns a copy of sp of the proper type with its stored pointer casted dynamically from U* to T*.
If sp is not empty, and such a cast would not return a null pointer, the returned object shares ownership over sp's resources, increasing by one the use count.
Otherwise, the returned object is an empty shared_ptr.
The function can only cast types for which the following expression would be valid:
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dynamic_cast<T*>(sp.get())
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Parameters
- sp
- A shared_ptr.
U* shall be convertible to T* using dynamic_cast.
Return Value
A shared_ptr object that owns the same pointer as sp (if any) and has a shared pointer that points to the same object as sp with a potentially different type.
Example
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// static_pointer_cast example
#include <iostream>
#include <memory>
struct A {
static const char* static_type;
const char* dynamic_type;
A() { dynamic_type = static_type; }
};
struct B: A {
static const char* static_type;
B() { dynamic_type = static_type; }
};
const char* A::static_type = "class A";
const char* B::static_type = "class B";
int main () {
std::shared_ptr<A> foo;
std::shared_ptr<B> bar;
bar = std::make_shared<B>();
foo = std::dynamic_pointer_cast<A>(bar);
std::cout << "foo's static type: " << foo->static_type << '\n';
std::cout << "foo's dynamic type: " << foo->dynamic_type << '\n';
std::cout << "bar's static type: " << bar->static_type << '\n';
std::cout << "bar's dynamic type: " << bar->dynamic_type << '\n';
return 0;
}
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Output:
foo's static type: class A
foo's dynamic type: class B
bar's static type: class B
bar's dynamic type: class B
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