templates: despite "this->" is a call to independent function not executed

[coder9911]

Hello,

below you find code for a few template classes.

In DisconnectedState::connect() you find in line 85 where this->castSomeEvent of the base class should be called. This call silently does not take place. Instead the call is simply skipped.

Any idea why?

Thank you!

class IHashable
{
	public:
	virtual ~IHashable(){}
	virtual uintmax_t getHashCode() const {
		return (uintmax_t) this;
	}
};

class IConnection : public IHashable
{
	public:
	virtual ~IConnection() {}
	virtual void connect(){throw "IConnection.connect: override this method!";}
	virtual void disconnect(){throw "IConnection.disconnect: override this method!";}
	virtual int receive(){throw  "IConnection.receive: override this method!";}
	virtual void send(int value){throw "IConnection.send: override this method!";}
};

class Event : public IHashable
{
public:
	Event(const char* name);
	virtual ~Event();
	string& getName();
private:
	string _name;
};

class IEventSink
{
	public:
		IEventSink(){}
		virtual ~IEventSink(){}
        virtual void castEvent(const Event& event) = 0;
};

template<class T>
class StateBase 
{
protected:
	T& automaton;
	IEventSink& eventSink;

public:
	StateBase(T& aAutomaton, IEventSink& aEventSink) :
	automaton(aAutomaton),
	eventSink(aEventSink)
	{
	}

	virtual ~StateBase(){}

	virtual void castSomeEvent(const Event& event) //// this is the method that I hoped would be called!
	{
		eventSink.castEvent(event);
	}

};

template<class T>
class DisconnectedState : public StateBase<T>, public IConnection 
{
public:

	static const Event CONNECT;
	static const Event ERROR;

	DisconnectedState(T& aAutomaton, IEventSink& aEventSink, Socket& aSocket)
		: StateBase<T>(aAutomaton, aEventSink),
	      socket(aSocket)
	{
	}

	virtual ~DisconnectedState(){}

	virtual void connect()
	{
		try	{
			socket.connect();
		} catch (...) {
			this->eventSink.castEvent(ERROR);
			throw;
		}
		this->castSomeEvent(CONNECT); // <<< this call is not executed; instead jump to ***
	}

	virtual void disconnect(){}

	virtual int receive()
	{
		throw new ConnectionClosedException("Can not receive: disconnected!");
	}


	virtual void send(int value)
	{
		throw new ConnectionClosedException("Can not send: disconnected!");
	}

protected:
	Socket& socket;
};


template<class AI>
const Event DisconnectedState<AI>::CONNECT("CONNECT");
template<class AI>
const Event DisconnectedState<AI>::ERROR("ERROR");
	
template<class AI>
class AutomatonBase : implements IEventSink
{
public:
	AutomatonBase()
	{
	}

	virtual ~AutomatonBase()
	{
	}

	virtual void castEvent(const Event& event)
	{
	}

protected:
	AI* pState;
};
	
class ConnectAutomaton : public AutomatonBase<IConnection>, public IConnection {
public:
	virtual ~ConnectAutomaton()
	{
		delete pSocket;
	}

	static ConnectAutomaton& createAutomaton() {
		ConnectAutomaton* pNew = new ConnectAutomaton();
		return *pNew;
	}

	virtual void connect()
	{
		pState->connect(); // call of DisconnectedState::connect() works fine.
	} // *** this is where we end up instead of calling the desired method at <<< above!
	
	virtual void disconnect()
	{
		pState->disconnect();
	}
	virtual int receive()
	{
		return pState->receive();
	}
	virtual void send(int value)
	{
		pState->send(value);
	}


private:
	ConnectAutomaton() : AutomatonBase<IConnection>(), IConnection()
	{
		pSocket = new Socket();

		pDisconnected = new DisconnectedState<IConnection>(*this, *this, *pSocket);

		this->pState = pDisconnected;
	}
	Socket* pSocket;
	IConnection* pDisconnected;

};

main() 
{
	ConnectAutomaton* pConnectAutomaton;
	ConnectAutomaton& ca = ConnectAutomaton::createAutomaton();
	pConnectAutomaton = &ca;
	pConnectAutomaton->connect();
}

[Snarky]

Hi! Could you edit your post to put the code within code blocks? That way you can refer to a specific line number that you are having problems with.

[Snarky]

Thanks! My guess would be that you are hitting that throw; call on line 83, at which point the function stops executing and looks for the catch handler?

[coder9911]

Thank you, Snarky!

The catch block is never executed. But commenting the try...catch()... out is the key!

Now line 85 calls the correct method. This behavior leaves me a bit puzzled nevertheless...