Delegate.h

/*
   Copyright (C) 2005 by Dr. Marc Boris Duerner
 
  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.
 
  As a special exception, you may use this file as part of a free
  software library without restriction. Specifically, if other files
  instantiate templates or use macros or inline functions from this
  file, or you compile this file and link it with other files to
  produce an executable, this file does not by itself cause the
  resulting executable to be covered by the GNU General Public
  License. This exception does not however invalidate any other
  reasons why the executable file might be covered by the GNU Library
  General Public License.
 
  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.
 
  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the:
  Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  Boston, MA 02110-1301 USA
*/
 
#ifndef Pt_Delegate_h
#define Pt_Delegate_h
 
#include <Pt/Void.h>
#include <Pt/Slot.h>
#include <Pt/Function.h>
#include <Pt/Method.h>
#include <Pt/ConstMethod.h>
#include <Pt/Connectable.h>
#include <stdexcept>
 
namespace Pt {
 
class DelegateBase : public Connectable
{
    public:
        DelegateBase()
        { }
 
        DelegateBase(const DelegateBase& rhs)
        { DelegateBase::operator=(rhs); }
 
        DelegateBase& operator=(const DelegateBase& other)
        {
            _target.close();
 
            if( other._target.isValid() )
            {
                const Slot* slot = other._target.slot();
                _target = Connection( *this, slot->clone()  );
            }
 
            return *this;
        }

        bool isConnected() const
        {
            return _target.isValid();
        }
 
        virtual void onConnectionOpen(const Connection& c)
        {
            const Connectable* sender = c.sender();
 
            if( sender == this )
            {
                _target.close();
                _target = c;
            }
 
            Connectable::onConnectionOpen(c);
        }
 
        virtual void onConnectionClose(const Connection& c)
        {
            Connectable::onConnectionClose(c);
        }
 
    protected:
        void disconnectSlot()
        {
            _target.close();
        }
 
        void disconnectSlot(const Slot& slot)
        {
            if( _target.isValid() && _target.slot()->equals(slot) )
            {
                _target.close();
            }
        }
 
    protected:
        Connection _target;
};

template <typename R, typename... As>
class Delegate : public DelegateBase
{
    public:
        typedef Callable<R, As...> CallableT;
 
    public:
        Delegate()
        { }

        Delegate(const Delegate& rhs)
        {
            DelegateBase::operator=(rhs);
        }

        Connection connect(const BasicSlot<R, As...>& slot)
        {
            return Connection(*this, slot.clone());
        }

        void disconnect()
        {
            DelegateBase::disconnectSlot();
        }

        void disconnect(const BasicSlot<R, As...>& slot)
        {
            DelegateBase::disconnectSlot(slot);
        }

        R call(As... args)
        {
            if( ! _target.isValid() )
                throw std::logic_error("Delegate::call(): Delegate not connected");
 
            const CallableT* callable =
                static_cast<const CallableT*>( _target.callable() );
            return callable->call(args...);
        }

        void invoke(As... args)
        {
            if( ! _target.isValid() )
                return;
 
            const CallableT* callable =
                static_cast<const CallableT*>( _target.callable() );
            callable->call(args...);
        }

        R operator()(As... args)
        {
            return this->call(args...);
        }
};

template <typename R, typename... As>
class DelegateSlot : public BasicSlot<R, As...>
{
    public:
        explicit DelegateSlot(Delegate<R, As...>& delegate)
        : _method(delegate, &Delegate<R, As...>::call)
        { }
 
        // inherit doc
        Slot* clone() const
        {
            return new DelegateSlot(*this);
        }
 
        // inherit doc
        virtual const Callback* callable() const
        {
            return &_method;
        }
 
        // inherit doc
        virtual void onConnect(const Connection& connection)
        {
            _method.object().onConnectionOpen(connection);
        }
 
        // inherit doc
        virtual void onDisconnect(const Connection& connection)
        {
            _method.object().onConnectionClose(connection);
        }
 
        // inherit doc
        virtual bool equals(const Slot& slot) const
        {
            const DelegateSlot* other = dynamic_cast<const DelegateSlot*>(&slot);
            return other && _method == other->_method;
        }
 
    private:
        Method<R, Delegate<R, As...>, As...> _method;
};

template <typename R, typename... As>
DelegateSlot<R, As...> slot(Delegate<R, As...>& delegate)
{
    return DelegateSlot<R, As...>(delegate);
}

template <typename R, typename... As>
Connection operator+=(Delegate<R, As...>& delegate, const BasicSlot<R, As...>& slot)
{
    return delegate.connect(slot);
}
 
} // namespace Pt
 
#endif