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<concept id="GUID-18EF9CFA-5080-5F89-89EC-C64897612D6B" xml:lang="en"><title>How

to clean up non-CBase classes</title><shortdesc/><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-DDB53FB1-7E70-45C6-93F8-76FBE03CA6FA"><title>Cleanup for a TAny*</title> <p>This example code shows cleanup

for a <codeph>TAny*</codeph>, in this case a <codeph>TText</codeph>. </p> <codeblock id="GUID-62C1326A-2C9F-5F57-AA1C-EA557D0FF4FE" xml:space="preserve">TText* buffer=(TText*) User::Alloc(100*sizeof(TText)); 

// create a buffer 

CleanupStack::PushL(buffer);

// push it to the cleanup stack: treated as TAny*

TPtr8 bufferPtr(buffer,100);  // create a pointer to the buffer

...

// use the buffer

useBufferL(bufferPtr);

...

// destroy the buffer on the cleanup stack

CleanupStack::PopAndDestroy();  

</codeblock> </section>

<section id="GUID-B2DF0D27-9520-4B7D-A8BC-1B4B1A80A714"><title>Cleanup support for an R class</title> <p>This example code

shows how to provide cleanup stack support for an <codeph>R</codeph> class.

To do this, a <codeph>TCleanupItem</codeph> object must be constructed with

a pointer to the object to clean up, and a pointer to a function that provides

cleanup for that object. The most effective way to do this is to define a <codeph>TCleanupItem</codeph> cast

operator in the class. </p> <codeblock id="GUID-FEFC12E2-0BE9-5AEF-89AE-E812651D8AD1" xml:space="preserve">// TCleanupItem operator for objects of this class

RExampleClass::operator TCleanupItem()

 {

 return TCleanupItem(Cleanup,this);

 }</codeblock> <codeblock id="GUID-5D448C6A-C919-5251-9AC1-139A6F3703FC" xml:space="preserve">...</codeblock> <codeblock id="GUID-92812389-ADAF-554B-BF5E-AA515DF4BFB5" xml:space="preserve">// cleanup function for use by cleanup stack

static void RExampleClass::Cleanup(TAny *aPtr)

 { 

 // Invoke the Close member on the RExampleClass at aPtr

 testConsole.Printf(_L("Doing cleanup.\n"));

 (static_cast<RExampleClass*>(aPtr))->Close();

 }

// Show use

void DoTheExampleL()

 {

 RExampleClass r;

 r.Open();

 // Because RExampleClass has an operator TCleanupItem()

 // pushing it is OK

 CleanupStack::PushL(r);

 // ...use r

 // possibly some operations that leave

 // PopAndDestroy() invokes RExampleClass::Cleanup()

 CleanupStack::PopAndDestroy();

 }

 </codeblock> <p><b>Notes</b> </p> <ul>

<li id="GUID-E8C0A2EF-AD7D-55C9-9805-ADA6072C18F0"><p>The operator returns

a <codeph>TCleanupItem</codeph> object which is constructed from a pointer

to the static member function which performs the class’s cleanup processing,

and a pointer to the object to be cleaned up. </p> </li>

<li id="GUID-83B10F9E-E07F-59BD-A1A4-62795F6EFF19"><p>The static member function

which provides the class’s cleanup processing must cast the <codeph>TAny*</codeph> pointer

into a pointer of the class to be cleaned up. This allows the class member

function to perform the cleanup </p> </li>

<li id="GUID-61BAAE8E-C8B4-5034-B4D1-3E31F790B54C"><p> <codeph>CleanupStack::PopAndDestroy()</codeph> removes

the item from the cleanupstack and invokes the cleanup function defined in

the <codeph>TCleanupItem</codeph> object. </p> </li>

<li id="GUID-53F43DCE-9260-5A71-9D59-AABD7916AE9E"><p>Remember that the <codeph>TCleanupItem</codeph> does <i>not</i> go

onto the cleanupstack. the <codeph>TCleanupItem</codeph> is a container for

the object that goes onto the cleanupstack. In this example, a pointer to

the <codeph>RExampleClass</codeph> is put on the cleanupstack. </p> </li>

</ul> </section>

</conbody></concept>