1 <?xml version="1.0" encoding="utf-8"?>

     2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->

     3 <!-- This component and the accompanying materials are made available under the terms of the License 

     4 "Eclipse Public License v1.0" which accompanies this distribution, 

     5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->

     6 <!-- Initial Contributors:

     7     Nokia Corporation - initial contribution.

     8 Contributors: 

     9 -->

    10 <!DOCTYPE task

    11   PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd">

    12 <task id="GUID-DCB8CA27-F64F-4B78-831D-F88B1AD7E38B" xml:lang="en"><title>Create

    13 the client class</title><prolog><metadata><keywords/></metadata></prolog><taskbody>

    14 <context>       <p>Create the client-side service support class, derived from <codeph>REikAppServiceBase</codeph>, <codeph>RApaAppServiceBase</codeph>, or a suitable System-GUI specialization of this class. This will have the

    15 following responsibilities:</p> <ul>

    16 <li><p>Implementing the client API </p></li>

    17 <li><p>Organizing calls to and from the server over IPC</p></li>

    18 <li><p>Any necessary security checks on the server. For example, restricting

    19 the data sent to a server having particular capabilities.</p></li>

    20 <li><p>Parameter checking from the server. Parameters returned from the server

    21 application must be checked to ensure that they are valid.</p></li>

    22 <li><p>Time-out support for IPC calls to the server.</p></li>

    23 </ul><p>The reason for these checks is that the client cannot be sure that

    24 the server application is using the appropriate server-side service support

    25 classes and may instead be trying to weaken the system by implementing the

    26 IPC handling itself.</p><p>This example shows the client interface for a chat

    27 service implemented in two parts. The active object class <codeph>CChatter</codeph> is

    28 the main client interface. It uses a class <codeph>RInterAppChat</codeph>,

    29 derived from <codeph>REikAppServiceBase</codeph>, which handles the client-side

    30 IPC for the chat service. </p><codeblock xml:space="preserve">class RInterAppChat : public REikAppServiceBase

    31     {

    32     public:

    33         TInt Send(const TDesC& aMessage);

    34         void Receive(TRequestStatus& aStatus, TDes& aMessage);

    35         void CancelReceive();

    36     private:

    37         TUid ServiceUid() const;

    38     };

    39 class MChatterReceiver

    40     {

    41     public:

    42         virtual void Receive(const TDesC&) = 0;

    43     };

    44 class CChatter : public CActive

    45     {

    46     public:

    47         CChatter(MChatterReceiver& aReceiver);

    48         ~CChatter();

    49         void ConstructL(TUid aAppUid);

    50         void SendL(const TDesC& aMsg);

    51     private:

    52         void Queue();

    53         void RunL();

    54         void DoCancel();

    55     public:

    56         RInterAppChat iSub;

    57         TBuf<KMaxMyMessage> iBuf;

    58         MChatterReceiver& iReceiver;

    59     };</codeblock></context>

    60 </taskbody></task>