How +to clean up non-CBase classes

Cleanup for a TAny*

This example code shows cleanup +for a TAny*, in this case a TText.

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(); +

Cleanup support for an R class

This example code +shows how to provide cleanup stack support for an R class. +To do this, a TCleanupItem 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 TCleanupItem cast +operator in the class.

// TCleanupItem operator for objects of this class +RExampleClass::operator TCleanupItem() + { + return TCleanupItem(Cleanup,this); + } ... // 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(); + } +

Notes

The operator returns +a TCleanupItem 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.
The static member function +which provides the class’s cleanup processing must cast the TAny* pointer +into a pointer of the class to be cleaned up. This allows the class member +function to perform the cleanup
CleanupStack::PopAndDestroy() removes +the item from the cleanupstack and invokes the cleanup function defined in +the TCleanupItem object.
Remember that the TCleanupItem does not go +onto the cleanupstack. the TCleanupItem is a container for +the object that goes onto the cleanupstack. In this example, a pointer to +the RExampleClass is put on the cleanupstack.