std::reference_wrapper
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< cpp | utility | functional
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Definido no cabeçalho <functional> | ||
template<class T > class reference_wrapper; | (desde C++11) | |
std::reference_wrapper modelo de classe é um CopyConstructible e wrapper CopyAssignable em torno de uma referência ao objeto ou referência a funcionar de T tipo. Instâncias de std::reference_wrapper são objectos (podem ser copiados ou armazenados em recipientes), mas são implicitamente conversível T&, de modo que eles podem ser usados como argumentos com as funções que o tipo subjacente por referência.Original:
Class template
std::reference_wrapper is a CopyConstructible and CopyAssignable wrapper around a reference to object or reference to function of type T. Instances of std::reference_wrapper are objects (can be copied or stored in containers), but they are implicitly convertible to T&, so that they can be used as arguments with the functions that take the underlying type by reference.The text has been machine-translated via Google Translate.
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Funções auxiliares std::ref e std::cref são muitas vezes utilizados para gerar
std::reference_wrapper objetos. Original:
Helper functions std::ref and std::cref are often used to generate
std::reference_wrapper objects. The text has been machine-translated via Google Translate.
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std::reference_wrapper também é usado para passar objetos para std::bind ou para o construtor de std::thread por referência.Original:
std::reference_wrapper is also used to pass objects to std::bind or to the constructor of std::thread by reference.The text has been machine-translated via Google Translate.
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Índice |
[editar]Tipos de membro
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 |
type | T |
result_type | O tipo de retorno T se T é uma função. Caso contrário, não definido Original: The return type of T if T is a function. Otherwise, not defined The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
argument_type | 1) se T é uma função ou ponteiro para função que recebe um argumento do tipo A1, então argument_type é A1.2) se T é um tipo de classe com um tipo T::argument_type membro, então argument_type é um apelido para issoOriginal: 1) if T is a function or pointer to function that takes one argument of type A1, then argument_type is A1.2) if T is a class type with a member type T::argument_type, then argument_type is an alias of thatThe text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
first_argument_type | 1) se T é uma função ou ponteiro para função que recebe dois argumentos do tipo s A1 e A2, então first_argument_type é A1.2) se Original: 1) if T is a function or pointer to function that takes two arguments of type s A1 and A2, then first_argument_type is A1.2) if 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 | 1) se T é uma função ou ponteiro para função que recebe dois argumentos do tipo s A1 e A2, então second_argument_type é A2.2) se T é um tipo de classe com um tipo T::second_argument_type membro, então first_argument_type é um apelido para issoOriginal: 1) if T is a function or pointer to function that takes two arguments of type s A1 and A2, then second_argument_type is A2.2) if T is a class type with a member type T::second_argument_type, then first_argument_type is an alias of thatThe text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
[editar]Funções de membro
armazena uma referência num objecto std::reference_wrapper novo Original: stores a reference in a new std::reference_wrapper object 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) | |
religa um std::reference_wrapper Original: rebinds a std::reference_wrapper 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) | |
acessa a referência armazenada Original: accesses the stored reference 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) | |
chama a função armazenada Original: calls the stored function 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) | |
[editar]Exemplo
Demonstra o uso de um recipiente como reference_wrapper de referências, o que torna possível o acesso ao mesmo recipiente utilizando vários índices
Original:
Demonstrates the use of reference_wrapper as a container of references, which makes it possible to access the same container using multiple indexes
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#include <algorithm>#include <list>#include <vector>#include <iostream>#include <functional> int main(){std::list<int> l ={-4, -3, -2, -1, 0, 1, 2, 3, 4}; std::vector<std::reference_wrapper<int>> v(l.begin(), l.end());std::random_shuffle(v.begin(), v.end()); std::vector<std::reference_wrapper<int>> v2(v.begin(), v.end());std::partition(v2.begin(), v2.end(), [](int n){return n<0;}); std::cout<<"Contents of the list: ";for(int n: l){std::cout<< n <<' ';}std::cout<<'\n'; std::cout<<"Contents of the list, shuffled: ";for(int i: v){std::cout<< i <<' ';}std::cout<<'\n'; std::cout<<"Shuffled elements, partitioned: ";for(int i: v2){std::cout<< i <<' ';}std::cout<<'\n';}
Saída:
Contents of the list: -4 -3 -2 -1 0 1 2 3 4 Contents of the list, shuffled: 0 -1 3 4 -4 1 -2 -3 2 Shuffled elements, partitioned: -3 -1 -2 -4 4 1 3 0 2
[editar]Veja também
(C++11) (C++11) | cria um std::reference_wrapper com um tipo de deduzir o seu argumento Original: creates a std::reference_wrapper with a type deduced from its argument 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) |
(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) |
