C++ - std::shared_ptr::get

C++ - std::shared_ptr::get

public member function - 公开成员函数
Defined in header - 定义于头文件

1. std::shared_ptr::get

element_type* get() const noexcept;

Get pointer.
获取指针。

Returns the stored pointer.
返回存储的指针。

The stored pointer points to the object the shared_ptr object dereferences to, which is generally the same as its owned pointer.
存储的指针指向 shared_ptr 对象解引用的对象，通常与其拥有的指针相同。

The stored pointer (i.e., the pointer returned by this function) may not be the owned pointer (i.e., the pointer deleted on object destruction) if the shared_ptr object is an alias (i.e., alias-constructed objects and their copies).

如果 shared_ptr 对象是别名 (i.e., alias-constructed objects and their copies)，则 stored pointer (i.e., the pointer returned by this function) 可能不是 owned pointer (i.e., the pointer deleted on object destruction)。

A shared_ptr may share ownership of an object while storing a pointer to another object. get() returns the stored pointer, not the managed pointer.
shared_ptr 可以在存储指向另一个对象的指针时共享对象的所有权。get() 返回存储的指针，而非被管理指针。

2. Parameters

none

3. Return value

The stored pointer.
element_type is a member type, alias of shared_ptr's template parameter (T).

4. Examples

4.1 std::shared_ptr::get

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

#include 
#include 

int main()
{
	int* p = new int(10);
	std::shared_ptr strong(p);

	if (strong.get() == p)
		std::cout << "strong and p point to the same location\n";

	// four ways of accessing the same address:
	std::cout << *strong.get() << "\n";
	std::cout << *(strong.get()) << "\n";
	std::cout << *strong << "\n";
	std::cout << *p << "\n";

	return 0;
}

strong and p point to the same location
10
10
10
10
请按任意键继续. . .

assignment [ə'saɪnmənt]：n. 任务，布置，赋值

4.2 std::shared_ptr::get

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

#include 
#include 

void output(std::string msg, int const* pint)
{
	std::cout << msg << *pint << "\n";
}

int main()
{
	int* pint = new int(10);
	std::shared_ptr pshared = std::make_shared(9);

	output("Naked pointer: ", pint);
	// output("Shared pointer ", pshared); // 编译错误
	output("Shared pointer with get(): ", pshared.get());

	delete pint;

	return 0;
}

1>------ Build started: Project: yongqiangcheng, Configuration: Debug Win32 ------
1>  yongqiang.cpp
1>d:\visual_studio_workspace\yongqiangcheng\yongqiangcheng\yongqiang.cpp(14): error C2679: binary '<<': no operator found which takes a right-hand operand of type 'std::string' (or there is no acceptable conversion)
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(495): note: could be 'std::basic_ostream> &std::basic_ostream>::operator <<(std::basic_streambuf> *)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(475): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(const void *)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(455): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(long double)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(435): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(double)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(415): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(float)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(395): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(unsigned __int64)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(375): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(__int64)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(355): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(unsigned long)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(335): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(long)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(315): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(unsigned int)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(290): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(int)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(270): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(unsigned short)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(236): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(short)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(216): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(bool)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(209): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(std::ios_base &(__cdecl *)(std::ios_base &))'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(202): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(std::basic_ios> &(__cdecl *)(std::basic_ios> &))'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(196): note: or       'std::basic_ostream> &std::basic_ostream>::operator <<(std::basic_ostream> &(__cdecl *)(std::basic_ostream> &))'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(692): note: or       'std::basic_ostream> &std::operator <<>(std::basic_ostream> &,const char *)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(739): note: or       'std::basic_ostream> &std::operator <<>(std::basic_ostream> &,char)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(777): note: or       'std::basic_ostream> &std::operator <<>(std::basic_ostream> &,const char *)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(824): note: or       'std::basic_ostream> &std::operator <<>(std::basic_ostream> &,char)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(950): note: or       'std::basic_ostream> &std::operator <<>(std::basic_ostream> &,const signed char *)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(957): note: or       'std::basic_ostream> &std::operator <<>(std::basic_ostream> &,signed char)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(964): note: or       'std::basic_ostream> &std::operator <<>(std::basic_ostream> &,const unsigned char *)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(971): note: or       'std::basic_ostream> &std::operator <<>(std::basic_ostream> &,unsigned char)'
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(981): note: or       'std::basic_ostream> &std::operator <<,std::string>(std::basic_ostream> &&,const _Ty &)'
1>          with
1>          [
1>              _Ty=std::string
1>          ]
1>  d:\program files (x86)\microsoft visual studio 14.0\vc\include\ostream(1019): note: or       'std::basic_ostream> &std::operator <<>(std::basic_ostream> &,const std::error_code &)'
1>  d:\visual_studio_workspace\yongqiangcheng\yongqiangcheng\yongqiang.cpp(14): note: while trying to match the argument list '(std::ostream, std::string)'
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

添加头文件 #include 。

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

#include 
#include 
#include 

void output(std::string msg, int const* pint)
{
	std::cout << msg << *pint << "\n";
}

int main()
{
	int* pint = new int(10);
	std::shared_ptr pshared = std::make_shared(9);

	output("Naked pointer: ", pint);
	// output("Shared pointer ", pshared); // 编译错误
	output("Shared pointer with get(): ", pshared.get());

	delete pint;

	return 0;
}

Naked pointer: 10
Shared pointer with get(): 9
请按任意键继续. . .

References

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