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std::ref, std::cref

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< cpp‎ | utility‎ | functional

 
 
 
Function-Objekte
Funktionswrapper
function(C++11)
mem_fn(C++11)
bad_function_call(C++11)
Bindung
bind(C++11)
is_bind_expression(C++11)
is_placeholder(C++11)
_1, _2, _3, ...(C++11)
Referenzwrapper
reference_wrapper(C++11)
ref
cref
(C++11)
(C++11)
Operatorwrapper
Verneinung
Veraltete Binder und Adapter
unary_function(veraltet)
binary_function(veraltet)
ptr_fun(veraltet)
pointer_to_unary_function(veraltet)
pointer_to_binary_function(veraltet)
mem_fun(veraltet)
mem_fun_t
mem_fun1_t
const_mem_fun_t
const_mem_fun1_t
(veraltet)
(veraltet)
(veraltet)
(veraltet)
mem_fun_ref(veraltet)
mem_fun_ref_t
mem_fun1_ref_t
const_mem_fun_ref_t
const_mem_fun1_ref_t
(veraltet)
(veraltet)
(veraltet)
(veraltet)
binder1st
binder2nd
(veraltet)
(veraltet)
bind1st
bind2nd
(veraltet)
(veraltet)
 
Defined in header <functional>
template< class T >
std::reference_wrapper<T> ref(T& t);
(1) (seit C++11)
template< class T >
std::reference_wrapper<T> ref( std::reference_wrapper<T> t );
(2) (seit C++11)
template< class T >
std::reference_wrapper<const T> cref( const T& t );
(3) (seit C++11)
template< class T >
std::reference_wrapper<const T> cref( std::reference_wrapper<T> t )
(4) (seit C++11)
Funktionsschablonen ref und cref sind Hilfsfunktionen, die ein Objekt vom Typ std::reference_wrapper erzeugen, mit Template-Argument Abzug der Template-Argument des Ergebnisses zu bestimmen .
Original:
Function templates ref and cref are helper functions that generate an object of type std::reference_wrapper, using template argument deduction to determine the template argument of the result.
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Inhaltsverzeichnis

[Bearbeiten] Parameter

t -
lvalue Verweis auf Objekt, umhüllt oder eine Instanz std::reference_wrapper muss
Original:
lvalue reference to object that needs to be wrapped or an instance of std::reference_wrapper
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[Bearbeiten] Rückgabewert

1) std::reference_wrapper<T>(t)

2) ref(t.get())

3) std::reference_wrapper<const T>(t)

4) cref(t.get())

[Bearbeiten] Ausnahmen

noexcept specification:  
noexcept
  (seit C++11)

[Bearbeiten] Beispiel

#include <functional>
#include <iostream>
 
void f(int& n1, int& n2, const int& n3)
{
    std::cout << "In function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
    ++n1; // increments the copy of n1 stored in the function object
    ++n2; // increments the main()'s n2
    // ++n3; // compile error
}
 
int main()
{
    int n1 = 1, n2 = 2, n3 = 3;
    std::function<void()> bound_f = std::bind(f, n1, std::ref(n2), std::cref(n3));
    n1 = 10;
    n2 = 11;
    n3 = 12;
    std::cout << "Before function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
    bound_f();
    std::cout << "After function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
}

Output:

Before function: 10 11 12
In function: 1 11 12
After function: 10 12 12

[Bearbeiten] Siehe auch

CopyConstructible und CopyAssignable Referenz-Wrapper
Original:
CopyConstructible and CopyAssignable reference wrapper
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(Klassen-Template) [edit]