Chapter 1

Figure 17.2
It is also worth mentioning here a change from Symbian OS v5. The CActive class now
provides an error handling function called RunError(). This is a virtual function for which
CActive provides a default implementation. The active scheduler calls the
RunError()function of an active object if a leave occurs in that object's RunL(). This will
be explained in more detail later in the chapter.
17.1.1 Construction and Destruction
Let's walk through the implementations of all the functions declared above. First, the easy
bits: here are two of the members involved in construction and destruction.
CDelayedHello* CDelayedHello::NewL()
{
CDelayedHello* self = new(ELeave) CDelayedHello;
CleanupStack::PushL(self);
self->ConstructL();
CleanupStack::Pop(self);
return self;
}
CDelayedHello::CDelayedHello()
: CActive(0)
{
CActiveScheduler::Add(this);
}
NewL() is a static function that follows the standard constructor- encapsulation pattern that
we saw in Chapter 6.
The C++ constructor is required for any derived active object class; inside it, you call
CActive's constructor to specify the active object's priority, which is used for tiebreaking
when more than one event occurs while another is being handled. You should specify zero
here unless there are good reasons to specify something lower or something higher. I'll
cover those reasons below. The new object adds itself to the active scheduler, so that the
active scheduler can include it in event handling.
void CDelayedHello::ConstructL()
{
iEnv = CEikonEnv::Static();
User::LeaveIfError(iTimer.CreateLocal());