std::reference_wrapper<T>::operator()
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< cpp | utility | functional | reference wrapper
template<class... ArgTypes> typenamestd::result_of<T&(ArgTypes&&...)>::type | (since C++11) (until C++17) | |
template<class... ArgTypes> std::invoke_result_t<T&, ArgTypes...> | (since C++17) (constexpr since C++20) | |
Calls the Callable object, reference to which is stored, as if by INVOKE(get(), std::forward<ArgTypes>(args)...). This function is available only if the stored reference points to a Callable object.
T must be a complete type.
Contents |
[edit]Parameters
| args | - | arguments to pass to the called function |
[edit]Return value
The return value of the called function.
[edit]Exceptions
May throw implementation-defined exceptions. | (since C++11) (until C++17) |
noexcept specification: noexcept(std::is_nothrow_invocable_v<T&, ArgTypes...>) | (since C++17) |
[edit]Example
Run this code
#include <functional>#include <iostream> void f1(){std::cout<<"reference to function called\n";} void f2(int n){std::cout<<"bind expression called with "<< n <<" as the argument\n";} int main(){std::reference_wrapper<void()> ref1 =std::ref(f1); ref1(); auto b =std::bind(f2, std::placeholders::_1);auto ref2 =std::ref(b); ref2(7); auto c =[]{std::cout<<"lambda function called\n";};auto ref3 =std::ref(c); ref3();}
Output:
reference to function called bind expression called with 7 as the argument lambda function called
[edit]Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3764 | C++17 | operator() is not noexcept | propagate noexcept |
[edit]See also
| accesses the stored reference (public member function) |
