std::function::target

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Utilities library

Type support (basic types, RTTI, type traits)

Dynamic memory management

Error handling

Program utilities

Variadic functions

Date and time

Function objects

initializer_list (C++11)

bitset

hash (C++11)

Relational operators

rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=

Pairs and tuples

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

integer_sequence (C++14)

Swap, forward and move

swap

exchange (C++14)

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

Function objects

Function wrappers
function (C++11)
mem_fn (C++11)
bad_function_call (C++11)
invoke (C++17)
Bind
bind (C++11)
is_bind_expression (C++11)
is_placeholder (C++11)
_1, _2, _3, ... (C++11)
Reference wrappers
reference_wrapper (C++11)
refcref (C++11)(C++11)
Operator wrappers
plus minus negate multiplies divides modulus logical_and logical_or logical_not	equal_to not_equal_to greater less greater_equal less_equal bit_and bit_or bit_xor bit_not (C++14)
Negators
unary_negate binary_negate	not1 not2
Deprecated binders and adaptors
unary_function (until C++17)
binary_function (until C++17)
ptr_fun (until C++17)
pointer_to_unary_function (until C++17)
pointer_to_binary_function (until C++17)
mem_fun (until C++17)
mem_fun_tmem_fun1_tconst_mem_fun_tconst_mem_fun1_t (until C++17)(until C++17)(until C++17)(until C++17)
mem_fun_ref (until C++17)
mem_fun_ref_tmem_fun1_ref_tconst_mem_fun_ref_tconst_mem_fun1_ref_t (until C++17)(until C++17)(until C++17)(until C++17)
binder1stbinder2nd (until C++17)(until C++17)
bind1stbind2nd (until C++17)(until C++17)

 

std::function

Member functions

function::function

function::~function

function::operator=

function::swap

function::assign

function::operator bool

function::operator()

function::target_type

function::target

Non-member functions

operator==operator!=

std::swap(std::function)

Helper classes

std::uses_allocator<std::function>

 

template< class T > T* target();	(1)	(since C++11)
template< class T > const T* target() const;	(2)	(since C++11)

Returns a pointer to the stored callable function target.

Parameters

(none)

Return value

A pointer to the stored function if target_type() == typeid(T), otherwise a null pointer.

Exceptions

noexcept specification:  

noexcept

  

Example

Run this code

#include <functional>
#include <iostream>
 
int f(int, int) { return 1; }
int g(int, int) { return 2; }
void test(std::function<int(int, int)> const& arg)
{
    std::cout << "test function: ";
    if (arg.target<std::plus<int>>())
        std::cout << "it is plus\n";
    if (arg.target<std::minus<int>>())
        std::cout << "it is minus\n";
 
    int (*const* ptr)(int, int) = arg.target<int(*)(int, int)>();
    if (ptr && *ptr == f)
        std::cout << "it is the function f\n";
    if (ptr && *ptr == g)
        std::cout << "it is the function g\n";
}
 
int main()
{
    test(std::function<int(int, int)>(std::plus<int>()));
    test(std::function<int(int, int)>(std::minus<int>()));
    test(std::function<int(int, int)>(f));
    test(std::function<int(int, int)>(g));
}

Output:

test function: it is plus
test function: it is minus
test function: it is the function f
test function: it is the function g

See also

target_type

obtains the typeid of the stored target (public member function)