Question

I am writing a NamedPipe extraction for C++11 and would like to have the following API*:

template<typename Mode>
class NamedPipe final {
    public:
        void Open();

        std::enable_if<Mode == Receiver>
        void Send();

        std::enable_if<Mode == Receiver>
        void Receive();

        void Close();
}

So that use looks like so:

NamedPipe<Sender> pipe_sender("test");
NamedPipe<Reciever> pipe_receiver("test");
pipe_sender.Open();
pipe_receiver.Open();
pipe_sender.Send("Some data");
pipe_receiver.Receive();
pipe_sender.Receive(); <--- compilation error

I have been using the type_traits in C++11 but only really just got into them – I’ve really enjoyed using them but this is really flexing the learning curve. Is there anyone with enough knowledge to point me in the right direction?

* the first example is deliberately rough as I keep going around in circles with the template stuff – I really just need to be put on the right path!

Answer 1

You can force compilation errors easily with static assertions:

template<typename Mode>
class NamedPipe final {
    public:
        void Open();    
        void Send();    
        void Receive();    
        void Close();
}        
template<typename Mode>
void NamedPipe<Mode>::Send() {
    static_assert(std::is_same<Mode, Sender>::value, "Cannot send from receivers");
    // blah blah implementation
}        
template<typename Mode>
void NamedPipe<Mode>::Receive() {
    static_assert(std::is_same<Mode, Receiver>::value, "Cannot receive with senders");
    // blah blah implementation
}

This not only gives compilation errors, but it gives nice descriptive errors.