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Symbian Developer Library

SYMBIAN OS V9.4

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Using CActive

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Writing derived classes

A CActive-derived class must fulfil a number of requirements, including providing a constructor and a number of functions.

To write a class which encapsulates an asynchronous service:

To write a class which handles the completion of an asynchronous request, a RunL() function should be provided. The function is defined as pure virtual in CActive and any class derived from CActive must define and implement it. RunL():

In some cases, a derived-class's RunL() will do some pre-handling of the request, and then invoke one or more appropriate virtual functions to handle particular types of completion. A further-derived class must provide virtual functions to specify the way various types of completion are handled.

In the general case, the derivation of a concrete active object from the CActive base class may involve

Depending on the circumstances, some of these stages of derivation may be amalgamated into one stage; or stages may be refined into even finer derivation stages.