unique_ptr smart pointers articles
Summary:
As a smart pointer, it was designed to address the most critical goal is native pointer lack of security issues
Declaration syntax:
std :: unique_ptr <type> variable name} {initialization value;
Precautions: best fit to initialize std :: make_unique unique_ptr
For example as follows:
The first:
// 初始化一个数据类型空间，括号内为初始化的值
std::unique_ptr<int> upa{ std::make_unique<int>(150) };
std::cout << "upa = " << *upa << std::endl;
result:
The second:
//初始化许多个数据类型空间，圆括号内为初始化空间个数,这里即可放10个int
std::unique_ptr<int[]> upb{ std::make_unique<int[]>(10) };
upb[0] = 10; upb[1] = 20; //一看就懂
std::cout << "upb[0] = " << upb[0] << " upb[1] = " << upb[1]<< std::endl;
result:
Important features:
Features of this unique pointer with his name, it can not make more than two unique pointer to the same memory address.
To the wrong example:
std::unique_ptr<int> upa{ std::make_unique<int>(20) }; //第一个unique指针
std::unique_ptr<int> upb{ upa }; //初始化时指向第一个，直接报错，编译过不去
Common methods:
1、get()
Description: Returns the unique native pointer! How to understand? please look below:
std::unique_ptr<int> upa{ std::make_unique<int>(20) };
int* pa = upa.get(); //定义一个原生指针接收它就可以了
std::cout << "pa=" << *pa << std::endl;
result:
2、reset()
Introduction: release unique memory space pointer, and the pointer to nullptr (c ++ 11 and above)
For example as follows:
std::unique_ptr<int> upa{ std::make_unique<int>(20) };
upa.reset(); //释放内存并且指向nullptr
std::cout << upa << std::endl;
result:
3、release()
Description: Returns the memory address of the original unique pointer, but the pointer to the unique space, how to understand?
For example as follows:
std::unique_ptr<int> upa{ std::make_unique<int>(20) };
std::cout << "原upa地址=" << upa << std::endl;
int * a = upa.release();
std::cout << "a地址="<< a << std::endl;
std::cout << "新upa地址=" << upa << std::endl;
result:
4、std::move(unique_ptr)
Description: In order to solve the uniqueness unique and can not be transferred to another unique characteristic of
For example as follows:
std::unique_ptr<int> upa{ std::make_unique<int>(20) };
std::unique_ptr<int> upb{};
std::cout << "原upa==" << upa << std::endl;
upb = std::move(upa);
std::cout << "upb==" << upb << std::endl;
std::cout << "新upa==" << upa << std::endl;
Results:
Precautions: method it is not a class, but the standard library function std; and get different is that he is transferred directly to Li Gang, a unique pointer, and get transferred to a native pointer!
sharedx_ptr smart pointers articles
Summary:
Is different from the unique, he can define a number of shared pointers point to the same address; intelligent in what place it? Only when the last shared pointer release, this memory will be released! And can record the current address how many smart pointer calls
Declaration syntax:
std :: sharedx_ptr <type> variable name} {initialization value;
Precautions: best fit to initialize std :: make_shared shared_ptr
For example as follows:
//第一种,跟unique一样的形式，只是把unique换成shared
std::shared_ptr<int> spa{ std::make_shared<int>(50) };
//第二种 这种方法不行，用第三种替换
//std::shared_ptr<int[]> spb{ std::make_shared<int[]>(4) };
//第三种 //用new申请数组形式替代即可
std::shared_ptr<int[]> spc{ new int[4]{1,2,3,4} };
Common methods:
1、use_count()
Description: returns the current address how many calls shared_ptr
Code:
std::shared_ptr<int> spa{ std::make_shared<int>(50) };
std::cout << spa.use_count() << std::endl; //1
std::shared_ptr<int> spb{ spa };
std::cout << spa.use_count() << std::endl; //2
std::shared_ptr<int> spc{ spa };
std::cout << spa.use_count() << std::endl; //3
result:
2、unique()
Summary:
原型： bool std::shared_ptr.unique();
Description: If the only shared_ptr pointing a pointer to the shared area, returns true, false otherwise
Code:
std::shared_ptr<int> spa{ std::make_shared<int>(50) };
std::cout << spa.unique() << " "; //唯一
std::shared_ptr<int> spb{ spa };
std::cout << spa.unique() << " "; //不唯一
std::shared_ptr<int> spc{ spa };
std::cout << spa.unique() << " "; //不唯一
result:
3、reset()
Description: Set the current share pointer nullptr, if the last one, it will free up memory
Code:
std::shared_ptr<int> spa{ std::make_shared<int>(50) };
std::shared_ptr<int> spb{ spa };
std::shared_ptr<int> spc{ spa };
spa.reset(); std::cout << spb << " "; //还没释放内存
spb.reset(); std::cout << spc << " ";//还没释放内存
spc.reset(); std::cout << spc << " ";//释放内存
Results:
Thanks again for your efforts and hard work! ! I feel that good old iron little bit like oh! I was sailing potatoes, thank you!
