Thread: An error saying 'no matching function call'; even when I declared the function

Here is the code....at a very nascent stage.

Code:

class net_device
{
    
    protected:
    bool send(net_device&,packet);
    std::deque<pack_dev_map> send_buffer;
    std::deque<pack_dev_map> recv_buffer;
    public:
    static bool connect(net_device,net_device);

};
//********/
class packet
{
    private:
    std::string main_data;
    //packet headers go here..
    public:
    std::string get_main_data();
    packet(std::string);
    //packet(packet&)
};
packet::packet(std::string data_arg)
{
    main_data = data_arg;
}


std::string packet::get_main_data()
{
    return main_data;
}
//*********/
class pack_dev_map //packet-device sets...did not use std::map
{
    public:
    packet p;
    net_device* n;
    pack_dev_map(packet&,net_device&);
};

pack_dev_map::pack_dev_map(packet& p_arg,net_device& n_arg)
{
    p = p_arg;
    n = &n_arg;
}

The bold lines show an error that packet:: packet() is not defined. It is not, but why does it need it ?

[also..to the moderators who may see this, I can't find a way to change the - now invalid- title of the post, can you do that?]

The article says that the member objects must gave a way to be initialized; I'm sending references of objects of those types for that purpose.
Shouldn't the default copy constructor and/0r the default assignment operator do the same job here ?

In other words:: Why must I use

pack_dev_map::pack_dev_map(packet& p_arg,net_device& n_arg):p(p_arg),n(&n_arg){}?

Creating a non default constructor will remove the default constructor.

Why do I need the default constructor here?
Isn't the default copy constructor/assignment operator enough for initializing ?

I don't want to keep a default constructor because there wouldn't be any default objects in the program.

The string constructor is enough if you use and initializer list, yes. But If you don't then the packet needs to be default-constructed before the body of the constructor is called.

In order to use a variable in the constructor, such as by assigning to it, it must be a valid object. That means it must already be constructed somehow. Lacking an initializer list, a no argument constructor is the only way.

This might also be of some use to you: SourceForge.net: Do not remove parameter names - cpwiki