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<concept id="GUID-3B0BF8FF-88AB-5BF4-9F04-5F82A3998699" xml:lang="en"><title>How

to store and restore a non-compound object</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<section><title> Storing</title> <p>The basic protocol for storing is the <codeph>StoreL()</codeph> function

and should be prototyped as:</p> <codeblock id="GUID-112220CB-F74B-59FA-8EF7-BA9D1C616860" xml:space="preserve">TStreamId StoreL(CStreamStore&amp; aStore) const;</codeblock> <p>The function takes a reference to the store in which the stream is to

be stored and returns the stream ID through which the object can be restored. </p> <p>In

some cases, the design of a class may be such that it maintains a pointer

or reference to the store. In this event, the <codeph>CStreamStore</codeph> argument

would be redundant.</p> <p>To store an object that does not contain any other

objects:</p> <ol id="GUID-1C25EAB3-DFBB-5486-B58D-45B4939A04FC">

<li id="GUID-18320343-D11D-59F4-A875-A7306E190864"><p>construct a write stream

object, i.e. an instance of <codeph>RStoreWriteStream</codeph> </p> </li>

<li id="GUID-DA4E34C4-CBC3-5C57-A329-CAA63053BC2D"><p>externalise the object</p> </li>

<li id="GUID-C6137D35-5525-56FF-8906-C5B3E8AD28CE"><p>return the ID of the

stream</p> </li>

</ol> <p>The following code fragment shows the canonical form for some general

class <codeph>CClassA</codeph>:</p> <codeblock id="GUID-3AA0A33A-940C-5315-813E-BC774D7F30A2" xml:space="preserve">TStreamId CClassA::StoreL(CStreamStore&amp; aStore) const

    {

    RStoreWriteStream stream;

    TStreamId id=stream.CreateLC(aStore);

    ExternalizeL(stream);

    stream.CommitL();

    CleanupStack::PopAndDestroy();

    return id;

    }</codeblock> </section>

<section><title>Restoring</title><p>The basic protocol for restoring is the

<code>RestoreL()</code>  function and should be prototyped as:

</p><codeblock xml:space="preserve">void RestoreL(CStreamStore&amp; aStore,TStreamId anId);</codeblock><p>The

function takes a reference to the store in which the stream is stored and

the ID that identifies that stream is stored.</p><p>To restore an object that

does not contain any other objects:</p><ul>

<li><p>construct a read stream object, i.e. an instance of</p><codeph>RStoreReadStream</codeph></li>

<li><p>internalise the object.</p></li>

</ul><p>The following code fragment shows an example for some general class</p><codeph>CClassA</codeph><codeblock xml:space="preserve">     void CClassA::RestoreL(CStreamStore&amp; aStore, TStreamId anId)

     {

          RStoreReadStream stream;

          stream.OpenLC(aStore,anId);

          InternalizeL(stream);

          CleanupStack::PopAndDestroy();

     }</codeblock><p/> </section>

</conbody></concept>