Getting the Object Type from a Shared Pointer in C++

user_7729842 0
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Is there a way to get the object type from a shared pointer? Suppose:

auto p = std::make_shared<std::string>("HELLO");

I want to get the string type from p i.e. something like:

p::element_type s = std::string("HELLO");

meaning: p::element_type is a std::string.

Thanks!

pointers shared-ptr object c++ types
2 Answers

shared_ptr::element_type gives you the type held by the shared_ptr; you can access this type from p using the decltype specifier. For example:

int main()
{
    auto p = std::make_shared<std::string>("HELLO");
    decltype(p)::element_type t = "WORLD"; // t is a std::string
    std::cout << *p << " " << t << std::endl;
}
user_5064130

as you've probably seen, per cppreference, std::shared_ptr has a type alias member_type = std::remove_extent_t<T>.

to access it, you can do something like

auto p = std::make_shared<std::string>("hello");
decltype(p)::element_type s = std::string{"heya"};

the type alias is associated to the class itself, not the specific member! godbolt

user_151443710
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