C++ - std::make_shared

C++ - std::make_shared

function template - 函數模板
Defined in header <memory> - 定義於頭文件 <memory>
creates a shared pointer that manages a new object. - 創建管理一個新對象的共享指針。

1. std::make_shared

template <class T, class... Args>
  shared_ptr<T> make_shared (Args&&... args);

Make shared_ptr.

Allocates and constructs an object of type T passing args to its constructor, and returns an object of type shared_ptr<T> that owns and stores a pointer to it (with a use count of 1).
分配並構造類型爲 T 的對象，將 args 傳遞給其構造函數，然後返回類型爲 shared_ptr<T> 的對象，該對象擁有並存儲指向它的指針 (使用計數爲 1)。

This function uses ::new to allocate storage for the object. A similar function, allocate_shared, accepts an allocator as argument and uses it to allocate the storage.
這個函數使用 ::new 爲對象分配存儲空間。類似的函數 allocate_shared 接受一個 allocator 作爲參數，並使用它來分配存儲空間。

2. Parameters

args
List of elements passed to T's constructor. - 傳遞給 T 的構造函數的元素列表。
Args is a list of zero or more types. - Args 是零個或多個類型的列表。

3. Return value

A shared_ptr object that owns and stores a pointer to a newly allocated object of type T.
一個 shared_ptr 對象，它擁有並存儲指向類型爲 T 的新分配對象的指針。

std::shared_ptr of an instance of type T.
類型 T 實例的 std::shared_ptr。

4. Examples

4.1 std::make_shared

//============================================================================
// Name        : std::make_shared
// Author      : Yongqiang Cheng
// Version     : Version 1.0.0
// Copyright   : Copyright (c) 2019 Yongqiang Cheng
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
#include <memory>

int main()
{
	std::shared_ptr<int> cheng = std::make_shared<int>(10);
	// same as:
	std::shared_ptr<int> strong(new int(10));

	auto yong = std::make_shared<int>(20);

	auto qiang = std::make_shared<std::pair<int, int>>(30, 40);

	std::cout << "*cheng: " << *cheng << '\n';
	std::cout << "*strong: " << *strong << '\n';
	std::cout << "*yong: " << *yong << '\n';
	std::cout << "*qiang: " << qiang->first << ' ' << qiang->second << '\n';

	return 0;
}

*cheng: 10
*strong: 10
*yong: 20
*qiang: 30 40
請按任意鍵繼續. . .

assignment [ə'saɪnmənt]：n. 任務，佈置，賦值

References

http://www.cplusplus.com/reference/memory/make_shared/
https://en.cppreference.com/w/cpp/memory/shared_ptr/make_shared