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Defined in header <any> | ||
template<class T,class...Args> std::any make_any( Args&&...args); | (1) | (since C++17) |
template<class T,class U,class...Args> std::any make_any(std::initializer_list<U> il, Args&&...args); | (2) | (since C++17) |
Constructs anany object containing an object of typeT, passing the provided arguments toT's constructor.
#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_castconst& 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_casta3.type() = "St8functionIFvvEE"Lambda #2.
constructs anany object(public member function)[edit] | |
(C++17) | type-safe access to the contained object (function template)[edit] |
