std::make_any
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Defined in header
<any>
template< class T, class... Args >
std::any make_any( Args&&... args );
(1)
(since C++17)
std::any make_any( Args&&... args );
template< class T, class U, class... Args >
std::any make_any( std::initializer_list <U> il, Args&&... args );
(2)
(since C++17)
std::any make_any( std::initializer_list <U> il, Args&&... args );
Constructs an any object containing an object of type T, passing the provided arguments to T's constructor.
1) Equivalent to return std::any (std::in_place_type <T>, std::forward <Args>(args)...);
2) Equivalent to return std::any (std::in_place_type <T>, il, std::forward <Args>(args)...);
[edit] Example
Run this code
#include <any> #include <complex> #include <functional> #include <iostream> #include <string> int main() { auto a0 = std::make_any<std::string >("Hello, std::any!\n"); auto a1 = std::make_any<std::complex <double>>(0.1, 2.3); std::cout << std::any_cast <std::string &>(a0); std::cout << std::any_cast <std::complex <double>&>(a1) << '\n'; using lambda = std::function <void(void)>; // Put a lambda into std::any. Attempt #1 (failed). std::any a2 = [] { std::cout << "Lambda #1.\n"; }; std::cout << "a2.type() = \"" << a2.type().name() << "\"\n"; // any_cast casts to <void(void)> but actual type is not // a std::function..., but ~ main::{lambda()#1}, and it is // unique for each lambda. So, this throws... try { std::any_cast <lambda>(a2)(); } catch (std::bad_any_cast const& ex) { std::cout << ex.what() << '\n'; } // Put a lambda into std::any. Attempt #2 (successful). auto a3 = std::make_any<lambda>([] { std::cout << "Lambda #2.\n"; }); std::cout << "a3.type() = \"" << a3.type().name() << "\"\n"; std::any_cast <lambda>(a3)(); }
Possible output:
Hello, std::any! (0.1,2.3) a2.type() = "Z4mainEUlvE_" bad any_cast a3.type() = "St8functionIFvvEE" Lambda #2.