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<concept xml:lang="en" id="GUID-36718217-C9F7-5ACF-8DE7-7D83FBF435DB"><title>Store map cleanup support</title><prolog><metadata><keywords/></metadata></prolog><conbody><p>The destructor of a <codeph>CStoreMap</codeph> object calls the <codeph>ResetAndDestroy()</codeph> member function. This function deletes from the store all streams whose stream IDs are currently held by the store map.</p> <p>This is of most use:</p> <ul><li id="GUID-1978575F-24D5-5B3A-8FED-5A067ACF5691"><p>in stores which do not support commit and revert, for example, the non-persistent in-memory store <codeph>CBufStore</codeph>.</p> </li> <li id="GUID-C8FBA74B-939B-576B-9443-D55AD9B798EC"><p>where the streams, whose IDs are in the store map, do not contain pointers to other streams.</p> </li> </ul> <p>This behaviour allows a partially complete set of streams to be deleted if a leave occurs part of the way through the building of the set.</p> <p>Note that this behaviour cannot be exploited by stores which do not support the deletion of streams, for example, the direct file store <codeph>CDirectFileStore</codeph>.</p> <p>Stores such as the permanent file store, <codeph>CPermanentFileStore</codeph>, can also use commit and revert to implement this kind of behaviour.</p> <p>Given the example class, <codeph>CCompound</codeph>, defined as:</p> <codeblock id="GUID-84E229C8-624C-5024-B25B-DB5957580775" xml:space="preserve">class CCompound : public CBase

    {

    ...

    TSwizzle<CClassA> iA;

    TSwizzle<CClassB> iB;

    TSwizzle<CClassC> iC; 

    ...

    }</codeblock> <p>the <codeph>CCompound</codeph> object is stored using its <codeph>StoreL()</codeph> function and the individual components are externalised by the <codeph>StoreComponentsL()</codeph> function:</p> <codeblock id="GUID-10BD78DC-C674-5C28-BECE-685A51324956" xml:space="preserve">TStreamId CCompound::StoreL(CStreamStore&amp; aStore)

    {

    CStoreMap* map=CStoreMap::NewLC(aStore);

    StoreComponentsL(*map);

       RStoreWriteStream stream(*map);

    TStreamId id=stream.CreateLC(aStore);

    ExternalizeL(stream);

    stream.CommitL();

    map->Reset();

    CleanupStack::PopAndDestroy(2);

    return id;

    }</codeblock> <codeblock id="GUID-8D249B61-5858-500D-A1A2-4C17FF9D0D63" xml:space="preserve">void CCompound::StoreComponentsL(CStoreMap&amp; aMap) const

    {

    TStreamId id;

    ...

    id = iA->StoreL(iStore);

    aMap.BindL(iA,id);

    ...

    id = iB->StoreL(iStore);

    aMap.BindL(iB,id);

    ...

    id = iC->StoreL(iStore);

    aMap.BindL(iC,id);

    ...