examples/Basics/MClasses1/MClasses1.cpp

/*
Copyright (c) 2000-2010 Nokia Corporation and/or its subsidiary(-ies). All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.
* Neither the name of Nokia Corporation nor the names of its contributors
  may be used to endorse or promote products derived from this software
  without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Description: 
Demonstrate use of M classes, or mixins - the
only use of multiple inheritance that has been
sanctioned by the E32 architecture team
This example shows how mixins can be used to
pass some protocol, and an associated object, from
a protocol provider to an protocol user.  The user
is not supposed to know everything about the provider,
only about the protocol it's interested in.
In this specific example, the provider is derived 
from a CProtocol class.
*/




#include "CommonFramework.h"

//
// -----> CProtocol (definition)
//
// A protocol class for mixing in
//
class CProtocol : public CBase
        {
public:
        virtual void HandleEvent(TInt aEventCode)=0;
        };


//
// -----> CProtocolUser (definition)
//
// Define a protocol user which uses this protocol
//
class CProtocolUser : public CBase
        {
public:
          // Construction
        static CProtocolUser* NewLC();
        static CProtocolUser* NewL();

          // Destruction
        ~CProtocolUser();

          // Some function which uses a protocol
        void DoSomething(CProtocol* aProtocol);

protected:
          // Construction assistance
        void ConstructL();
        };


//
// -----> CProtocolProvider (definition)
//
// A simple class which uses the mixin
//
class CProtocolProvider : public CProtocol
        {
public:
          // Construction
        static CProtocolProvider* NewLC();

          // Destruction
        ~CProtocolProvider();

          // Calls the protocol user
        void CallProtocolUser();

          // Implement the protocol (handles the protocol)
        void HandleEvent(TInt aEventCode);

protected:
          // Construction assistance
        void ConstructL();

private:
          // data member defined by this class
        CProtocolUser* iProtocolUser;
        };


//
// -----> CProtocolUser (implementation)
//
CProtocolUser* CProtocolUser::NewLC()
        {
        CProtocolUser* self=new(ELeave) CProtocolUser;
        CleanupStack::PushL(self);
        self->ConstructL();
        return self;
        }

CProtocolUser* CProtocolUser::NewL()
        {
        CProtocolUser* self=NewLC();
        CleanupStack::Pop();
        return self;
        }

CProtocolUser::~CProtocolUser()
        {
        }

void CProtocolUser::ConstructL()
        {
        }

void CProtocolUser::DoSomething(CProtocol* aProtocol)
        {
          // Do something that requires a protocol
        _LIT(KTxtExtSystemDoing,"External system doing something\n");
        console->Printf(KTxtExtSystemDoing);
        _LIT(KTxtInvokingProtocol,"invoking protocol - event 3\n");
        console->Printf(KTxtInvokingProtocol);
          // Handle an event
        aProtocol->HandleEvent(3);
        }


//
// -----> CProtocolProvider (implementation)
//
CProtocolProvider* CProtocolProvider::NewLC()
        {
        CProtocolProvider* self=new(ELeave) CProtocolProvider;
        CleanupStack::PushL(self);
        self->ConstructL();
        return self;
        };

CProtocolProvider::~CProtocolProvider()
        {
        delete iProtocolUser;
        }

void CProtocolProvider::ConstructL()
        {
        iProtocolUser=CProtocolUser::NewL();
        }

void CProtocolProvider::CallProtocolUser()
        { 
          // Call the protocol user to do some work
        _LIT(KTxtCallProtUser,"CProtocolProvider calling protocol user\n");
        console->Printf(KTxtCallProtUser);
        iProtocolUser->DoSomething(this);

                        // pass ourselves, disguised as our (unique)
                        // base class, so the protocol can be called
                        // back by the protocol user
        }

void CProtocolProvider::HandleEvent(TInt aEventCode)
        { 
          // A concrete implementation of the abstract protocol.
          // Handle an event in the protocol user
        _LIT(KFormat1,"CProtocolProvider handling event %d\n");
        console->Printf(KFormat1,aEventCode);
        }


//
// Do the example
//
LOCAL_C void doExampleL()
    {
          // show use of mixin with simple class
        CProtocolProvider* simpleProvider=CProtocolProvider::NewLC();
          // call protocol user
        simpleProvider->CallProtocolUser();
          // Remove simpleProvider from cleanup stack and destroy
        CleanupStack::PopAndDestroy();
        }

---