如何列出share_ptr？

Question

I am facing a design issue that could be summarized by the following class: A linked list of shared buffer where the linking element is a SharedBuffer

class SharedBuffer : public shared_ptr<Buffer> {
private:
    SharedBuffer    _next;

    SharedBuffer(Buffer* buffer) : shared_ptr<Buffer>(buffer) {}
    ~SharedBuffer() { 
        if (_next)
           _next.reset();
    }
}; 

This class is wrong because it references itself in its own definition. But that the idea. Any idea on making such a list of shared buffer?

Answer 1

The short answer is

You don't

There are many container classes in the stl. std::vector<> , std::list<> or whatever other container you are looking for. Do not roll your own. Please. You will only make mistakes and your time could be better spent working on your program logic instead of debugging a bad implementation of something, especially when good implementations are available for free.

std::vector<std::shared_ptr<Buffer>> sharedBuffers;

Answer 2

If your SharedBuffer really should stay a Shared object, just like shared_ptr is a shared "object" (object being pointer here, and sharing means shared ownership), but you want to have it reference-counted, you could simply hold a shared_ptr inside it rather than inheriting (which is a bad idea, especially considering the problems leading up to make_shared ).

class SharedBuffer {
private:
    std::shared_ptr<Buffer> _buffer;
    SharedBuffer            _next;

    SharedBuffer(Buffer* buffer) : _buffer{buffer} {}

    // note the following is now redundant, since it happens automatically
    /*~SharedBuffer() { 
        if (_next)
           _next.reset();
    }*/

    /* Other protected operations (e.g. read/write) */
}; 

Even better, you should already accept a shared_ptr in SharedBuffer 's constructor.