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C++自学24:唯一智能指针

尽量使用std::make_unique和std::make_shared而不直接使用new（总结)

使用

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std::unique_ptr<int> a = std::make_unique<int>(666); // 智能指针具有唯一性
std::unique_ptr<int> b = std::make_shared<int>(666);
// create std::initializer_list
auto initList = { 10, 20 };
// create std::vector using std::initializer_list ctor
auto spv = std::make_shared<std::vector<int>>(initList);

make_queue

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#include <iostream>
#include <iomanip>
#include <memory>
 
struct Vec3
{
    int x, y, z;
 
    // following constructor is no longer needed since C++20
    Vec3(int x = 0, int y = 0, int z = 0) noexcept : x(x), y(y), z(z) { }
 
    friend std::ostream& operator<<(std::ostream& os, const Vec3& v) {
        return os << "{ x=" << v.x << ", y=" << v.y << ", z=" << v.z << " }";
    }
};
 
int main()
{
    // Use the default constructor.
    std::unique_ptr<Vec3> v1 = std::make_unique<Vec3>();
    // Use the constructor that matches these arguments
    std::unique_ptr<Vec3> v2 = std::make_unique<Vec3>(0,1,2);
    // Create a unique_ptr to an array of 5 elements
    std::unique_ptr<Vec3[]> v3 = std::make_unique<Vec3[]>(5);
 
    std::cout << "make_unique<Vec3>():      " << *v1 << '\n'
              << "make_unique<Vec3>(0,1,2): " << *v2 << '\n'
              << "make_unique<Vec3[]>(5):   ";
    for (int i = 0; i < 5; i++) {
        std::cout << std::setw(i ? 30 : 0) << v3[i] << '\n';
    }
}