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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

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

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

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

    15 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

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

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

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

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

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

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

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

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

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

    25 stream</p> </li>

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

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

    28     {

    29     RStoreWriteStream stream;

    30     TStreamId id=stream.CreateLC(aStore);

    31     ExternalizeL(stream);

    32     stream.CommitL();

    33     CleanupStack::PopAndDestroy();

    34     return id;

    35     }</codeblock> </section>

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

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

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

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

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

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

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

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

    44 </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)

    45      {

    46           RStoreReadStream stream;

    47           stream.OpenLC(aStore,anId);

    48           InternalizeL(stream);

    49           CleanupStack::PopAndDestroy();

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

    51 </conbody></concept>