std::vector::emplace_back

 

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std::vector

Member-Funktionen Original: Member functions 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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Elementzugriff zerstört Original: Element access 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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Iteratoren Original: Iterators 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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Kapazität Original: Capacity 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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template<class... Args> void emplace_back( Args&&... args);		(seit C++11)

Fügt ein neues Element am Ende des Behälters. Das Element in-place ist so aufgebaut, dh kein Kopieren oder Verschieben von Operationen durchgeführt werden. Der Konstruktor des Elements wird mit genau den gleichen Argumenten, die an die Funktion geliefert werden genannt .

Original:

Appends a new element to the end of the container. The element is constructed in-place, i.e. no copy or move operations are performed. The constructor of the element is called with exactly the same arguments that are supplied to the function.

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If the new size() is greater than capacity(), all iterators and references are invalidated. Otherwise no iterators and references are invalidated.

Parameter

args

-

Argumente, die an den Konstruktor des Elements weiterzuleiten Original: arguments to forward to the constructor of the element The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Rückgabewert

(None)

Original:

(none)

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Komplexität

Constant .

Original:

Constant.

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Beispiel

Der folgende Code verwendet emplace_back ein Objekt vom Typ President einer std::vector anhängen. Es zeigt, wie emplace_back vorne Parameter an die President Konstruktor und zeigt, wie mit emplace_back vermeidet die zusätzlichen Kopieren oder Verschieben erforderlich, wenn push_back .

Original:

The following code uses emplace_back to append an object of type President to a std::vector. It demonstrates how emplace_back forwards parameters to the President constructor and shows how using emplace_back avoids the extra copy or move operation required when using push_back.

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#include <vector>#include <string>#include <iostream>   struct President {std::string name;std::string country;int year;   President(std::string&& p_name, std::string&& p_country, int p_year): name(std::move(p_name)), country(std::move(p_country)), year(p_year){std::cout<<"I am being constructed.\n";} President(President&& other): name(std::move(other.name)), country(std::move(other.country)), year(other.year){std::cout<<"I am being moved.\n";} President& operator=(const President& other)=default;};   int main(){std::vector<President> elections;std::cout<<"emplace_back:\n"; elections.emplace_back("Nelson Mandela", "South Africa", 1994);   std::vector<President> reElections;std::cout<<"\npush_back:\n"; reElections.push_back(President("Franklin Delano Roosevelt", "the USA", 1936));   std::cout<<"\nContents:\n";for(President const& president: elections){std::cout<< president.name<<" was elected president of "<< president.country<<" in "<< president.year<<".\n";}for(President const& president: reElections){std::cout<< president.name<<" was re-elected president of "<< president.country<<" in "<< president.year<<".\n";}}

Output:

emplace_back: I am being constructed.   push_back: I am being constructed. I am being moved.   Contents: Nelson Mandela was elected president of South Africa in 1994. Franklin Delano Roosevelt was re-elected president of the USA in 1936.

Siehe auch

push_back	fügt Elemente am Ende Original: adds elements to the end The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (öffentliche Elementfunktion)