std::mem_fn

 

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mem_fn (C++11)
bad_function_call (C++11)
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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
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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)

 

definiert in Header <functional>
template<class R, class T > /*unspecified*/ mem_fn(R T::* pm);	(1)	(seit C++11)
template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)const); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)volatile); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)constvolatile); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)&); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)const&); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)volatile&); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)constvolatile&); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)&&); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)const&&); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)volatile&&); template<class R, class T, class... Args> /*unspecified*/ mem_fn(R (T::* pm)(Args...)constvolatile&&);	(2)	(c + 11, jedoch Defekt)

Funktions-Template std::mem_fn generiert Wrapper Objekte für Zeiger auf Elemente, die gespeichert werden können, kopieren, und rufen Sie einen Zeiger auf ein Element. Beide Referenzen und Zeigern (einschließlich Smart Pointer) zu einem Objekt kann beim Aufrufen eines std::mem_fn werden .

Original:

Function template std::mem_fn generates wrapper objects for pointers to members, which can store, copy, and invoke a pointer to member. Both references and pointers (including smart pointers) to an object can be used when invoking a std::mem_fn.

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Die Überladungen (2) werden als defekt gemeldet .

Original:

The overloads (2) are reported as defect.

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Die resolution, die vor kurzem zum "Versuchsweise Ready" schlägt alle Überladungen (2) entfernen .

Original:

The resolution, which has recently been voted "Tentatively Ready" proposes to remove all the overloads (2).

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Dies wird einige Code zu brechen, siehe Beispiel 3 .

Original:

This will break some code, see Example 3.

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Parameter

pm

-

Zeiger auf ein Element, das verpackt werden soll Original: pointer to member that will be wrapped The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Rückgabewert

std::mem_fn gibt einen Anruf Wrapper angegebenen Typ, der die folgenden Mitglieder hat:

Original:

std::mem_fn returns an call wrapper of unspecified type that has the following members:

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std :: mem_fn

Original:

std::mem_fn

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Return type

Member types

Typ Original: type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.	definition
result_type	der Rückgabetyp pm wenn pm ist ein Zeiger auf Member-Funktion, nicht für Zeiger auf Member-Objekt definiert Original: the return type of pm if pm is a pointer to member function, not defined for pointer to member object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
argument_type	T*, möglicherweise cv-qualifiziert, wenn pm ein Zeiger auf Member-Funktion ohne Argumente ist Original: T*, possibly cv-qualified, if pm is a pointer to member function taking no arguments The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
first_argument_type	T* wenn pm ist ein Zeiger auf Member-Funktion ein Argument Original: T* if pm is a pointer to member function taking one argument The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
second_argument_type	T1 wenn pm ist ein Zeiger auf Member-Funktion ein Argument vom Typ T1 Original: T1 if pm is a pointer to member function taking one argument of type T1 The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Member function

operator()	ruft das Ziel auf einem bestimmten Objekt, mit optionalen Parametern Original: invokes the target on a specified object, with optional parameters The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (öffentliche Elementfunktion)

Ausnahmen

None .

Original:

None.

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Beispiel 1

Verwenden mem_fn zu speichern und auszuführen eine Member-Funktion und ein Mitglied Objekt:

Original:

Use mem_fn to store and execute a member function and a member object:

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#include <functional>#include <iostream>   struct Foo {void display_greeting(){std::cout<<"Hello, world.\n";}void display_number(int i){std::cout<<"number: "<< i <<'\n';}int data =7;};   int main(){ Foo f;   auto greet = std::mem_fn(&Foo::display_greeting); greet(f);   auto print_num = std::mem_fn(&Foo::display_number); print_num(f, 42);   auto access_data = std::mem_fn(&Foo::data);std::cout<<"data: "<< access_data(f)<<'\n';}

Output:

Hello, world. number: 42 data: 7

Beispiel 2

Übergeben Sie eine Member-Funktion in std::transform eine Folge von Zahlen zu erstellen:

Original:

Pass a member function to std::transform to create a sequence of numbers:

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#include <iostream>#include <functional>#include <iterator>#include <memory>#include <string>#include <vector>#include <algorithm>   int main(){std::vector<std::string> words ={"This", "is", "a", "test"};std::vector<std::unique_ptr<std::string>> words2; words2.emplace_back(new std::string("another")); words2.emplace_back(new std::string("test"));   std::vector<std::size_t> lengths;std::transform(words.begin(), words.end(), std::back_inserter(lengths), std::mem_fn(&std::string::size));// uses references to stringsstd::transform(words2.begin(), words2.end(), std::back_inserter(lengths), std::mem_fn(&std::string::size));// uses unique_ptr to strings   std::cout<<"The string lengths are ";for(auto n : lengths)std::cout<< n <<' ';std::cout<<'\n';}

Output:

The string lengths are 4 2 1 4 7 4

Beispiel 3

#include <functional>   struct X {int x;   int& easy(){return x;}int& get(){return x;}constint& get()const{return x;}};     int main(void){auto a = std::mem_fn(&X::easy);// no problem at all// auto b = std::mem_fn<int& >(&X::get ); // no longer works with new specificationauto c = std::mem_fn<int&()>(&X::get);// works with both old and new specificationauto d =[](X& x){return x.get();};// another approach to overload resolution}

Siehe auch

function (C++11)	wickelt aufrufbare Objekt eines beliebigen Typs mit dem angegebenen Funktion Call-Signatur Original: wraps callable object of any type with specified function call signature The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Klassen-Template)
bind (C++11)	bindet ein oder mehrere Argumente an eine Funktion Objekt Original: binds one or more arguments to a function object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktions-Template)