Calling a derived class method from the parent class' same method - c++

Question

My problem goes as follow: I am writing an extensible communication protocol between a server and a client. The objects needed to be transferred are using the command design pattern.
Here is the class format:
class command {
public:
using id = uint8_t;
using buffer = std::vector<char>;
enum command_t: id {a_command, another_command};
command() = delete;
command(id id): id_(id) {}
static command* unserialize(buffer);
virtual buffer const serialize() const = 0;
virtual void execute() = 0;
protected:
/* Not possible, see further where I explain. Keeping it here for
my example */
virtual static command* do_unserialize(buffer::iterator, buffer::iterator) = 0;
id id_;
};
class a_command;
class another_command;
Every command will be a subclass of command. A command_t id will be associated with every command. In the example above, a_command and another_command would have a respective class too.
command::serialize is implemented in the derived classes. What it does is it writes all the needed informations of the class in a byte array and returns it. Of course, the same thing goes for the protected command::do_unserialize - it takes a byte array and converts it to a command of the right type. But here is the problem:
The first byte of the buffer will always be the command::id associated with the good subclass.
When the server/client will receive data, it will read the command ID and then it needs to be able to unserialize it to the right command type. This is why it will need to call the static function command::unserialize and not one of the subclasses' do_unserialize.
A quick and dirty fix would be a command::unserialize looking like this:
command* command::unserialize(buffer b) {
auto it{b.begin()};
command::id const id{*it++};
switch(static_cast<command::command_t>(id)) {
case command::command_t::a_command:
return a_command::do_unserialize(it, b.end());
case command::command_t::another_command:
return another_command::do_unserialize(it, b.end());
default:
throw std::invalid_argument("command::unserialize: unknown command ID");
}
}
*** Actually not even, you cannot have a virtual static member function. So I have no idea how it could be implemented.
Even if it worked, it is not really fun, because it implies having to duplicate a line of code
for every new command created.
EDIT: A working example would be to move do_unserialize to the subclass constructor and return a pointer to the newly created object.
class derived_command: public command {
public:
derived_command(buffer::iterator beg, buffer::iterator end) {
// do_unserialize logic
}
};
// unserialize
switch (id) {
case command::command_t::derived_class: return new derived_class(b.begin(), b.end());
}
// ...
My question thus goes like this: Is there a way to dynamically link new commands only from the command::id field? A way to deduce the subclass to use from its ID? Else, is my design flawed? Is there a better way to do what I'm trying to do?
Thank you!