c++ - 重新创建(重新分配)一个 std::shared_ptr 或 std::unique_ptr

Question

我想要一个托管指针(唯一的或共享的)，并能够用新的内存重新分配它，并确保用托管指针删除旧内存(正如它应该的那样)。

struct MyStruct
{
       MyStruct(signed int) { }
       MyStruct(unsigned float) { }
};
std::unique_ptr<MyStruct> y(new MyStruct(-4)); // int instance
std::shared_ptr<MyStruct> x(new MyStruct(-5));

// do something with x or y
//...


// until now pointers worked as "int" next we want to change it to work as float

x = new MyStruct(4.443);
y = new MyStruct(3.22); // does not work

我如何以最简洁的方式实现这一点？

Answer 1

您有多种选择:

x = std::unique_ptr<MyStruct>(new MyStruct(4.443));
x = std::make_unique<MyStruct>(4.443); // C++14
x.reset(new MyStruct(4.443));

y = std::shared_ptr<MyStruct>(new MyStruct(3.22));
y = std::make_shared<MyStruct>(3.22);
y.reset(new MyStruct(3.22));