std::mem_fn

 

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Os operadores relacionais Original: Relational operators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

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

Pares e tuplas Original: Pairs and tuples The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

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Objetos de função

Invólucros de função Original: Function wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
function (C++11)
mem_fn (C++11)
bad_function_call (C++11)
Ligar Original: Bind The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
bind (C++11)
is_bind_expression (C++11)
is_placeholder (C++11)
_1, _2, _3, ... (C++11)
Invólucros de referência Original: Reference wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
reference_wrapper (C++11)
refcref (C++11)(C++11)
Invólucros operador Original: Operator wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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
Negadores Original: Negators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
unary_negate binary_negate	not1 not2
Obsoleta ligantes e adaptadores Original: Deprecated binders and adaptors The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
unary_function (obsoleta)
binary_function (obsoleta)
ptr_fun (obsoleta)
pointer_to_unary_function (obsoleta)
pointer_to_binary_function (obsoleta)
mem_fun (obsoleta)
mem_fun_tmem_fun1_tconst_mem_fun_tconst_mem_fun1_t (obsoleta)(obsoleta)(obsoleta)(obsoleta)
mem_fun_ref (obsoleta)
mem_fun_ref_tmem_fun1_ref_tconst_mem_fun_ref_tconst_mem_fun1_ref_t (obsoleta)(obsoleta)(obsoleta)(obsoleta)
binder1stbinder2nd (obsoleta)(obsoleta)
bind1stbind2nd (obsoleta)(obsoleta)

 

Definido no cabeçalho <functional>
template<class R, class T > /*unspecified*/ mem_fn(R T::* pm);	(1)	(desde 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, mas defeito)

std::mem_fn modelo função gera objetos wrapper para ponteiros para os membros, que pode armazenar, copiar, e chamar um ponteiro para membro. Ambas as referências e ponteiros (incluindo ponteiros inteligentes) para um objeto pode ser usado quando invocando um std::mem_fn.

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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As sobrecargas (2), são relatados como defeito.

Original:

The overloads (2) are reported as defect.

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O resolution, que foi recentemente eleito o "Timidamente Ready" propõe a eliminação de todas as sobrecargas (2).

Original:

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

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Isso vai quebrar um código, consulte Exemplo 3.

Original:

This will break some code, see Example 3.

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Parâmetros

pm

-

ponteiro para membro que será envolvido 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.

Valor de retorno

std::mem_fn retorna um invólucro chamada de tipo não especificado, que tem os seguintes membros:

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

tipo 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	o tipo de retorno pm se pm é um ponteiro para função de membro, não definido para ponteiro para objeto membro 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*, possivelmente cv qualificado, se pm é um ponteiro para função de membro não recebendo nenhum argumento 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* se pm é um ponteiro para função de membro recebendo um argumento 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 se pm é um ponteiro para função de membro recebendo um argumento do tipo 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()	invoca o alvo em um objeto determinado, com parâmetros opcionais 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. (função pública membro)

Exceções

Nenhum.

Original:

None.

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Exemplo 1

Use mem_fn para armazenar e executar uma função de membro e um objeto membro:

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';}

Saída:

Hello, world. number: 42 data: 7

Exemplo 2

Passe uma função de membro para std::transform para criar uma seqüência de números:

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';}

Saída:

The string lengths are 4 2 1 4 7 4

Exemplo 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}

Veja também

function (C++11)	envolve objeto que pode ser chamado de qualquer tipo com a assinatura especificada função chamada 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. (modelo de classe)
bind (C++11)	se liga um ou mais argumentos para um objeto de função 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. (modelo de função)