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

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

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

<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

following responsibilities:</p> <ul>

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    {

    public:

        TInt Send(const TDesC& aMessage);

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

        void CancelReceive();

    private:

        TUid ServiceUid() const;

    };

class MChatterReceiver

    {

    public:

        virtual void Receive(const TDesC&) = 0;

    };

class CChatter : public CActive

    {

    public:

        CChatter(MChatterReceiver& aReceiver);

        ~CChatter();

        void ConstructL(TUid aAppUid);

        void SendL(const TDesC& aMsg);

    private:

        void Queue();

        void RunL();

        void DoCancel();

    public:

        RInterAppChat iSub;

        TBuf<KMaxMyMessage> iBuf;

        MChatterReceiver& iReceiver;

    };</codeblock></context>

</taskbody></task>