I successfully addressed my QMutex/QWaitCondition breakage by refactoring my
termination chain. By sending a 'last call' down my class hierarchy, I was
able to give the threads the time they needed to actually end gracefully, and
release their resources.
However, while implementing this, I did discover that Qt signals cannot be
virtualized, and I wanted to just confirm that in certain circumstances (mine
in particular), they can actually mess with OOD. Let me explain.
Given a class Channel:
class Channel : public QObject
{
...
Channel();
signals:
void signal_channel_clear();
...
}
and given a class Client that contains a class Channel:
class Client : public QObject
{
...
Client(QSharedPointer<Channel> channel_pointer);
signals:
void signal_client_clear();
protected slots:
void slot_channel_clear(); // to receive Channel::signal_channel_clear
...
}
then given a subclass of Channel:
class SubChannel : public Channel
{
...
SubChannel();
signals:
void signal_channel_clear();
...
}
If I connect Channel::signal_channel_clear() to Client::slot_channel_clear()
when Client is passed a Channel pointer of type SubChannel:
connect(channel_pointer.data(), &Channel::signal_channel_clear, this,
&Client::slot_channel_clear);
then Client will never receive the signal when it is emitted from the
SubChannel class (because it was bound to Channel::signal_channel_clear).
Instead, from what I can fathom, I have to either dynamically cast SubChannel
within Client (very ugly, because Client doesn't know about SubChannel and may
not even have access to its header), or I have to make the Client slot public,
and at a level above them all, make the connections on their behalf,
increasing the coupling level:
QSharedPointer<SubChannel> subchannel = QSharedPointer(new SubChannel());
QSharedPointer<Client> client = QSharedPointer(new Client(subchannel));
connect(client.data(), &Client::slot_channel_clear, subchannel.data(),
&SubChannel::signal_channel_clear);
Basically, then, I wanted to know if this was the proper/only way to achieve
this, of if there was something obvious I'm overlooking? Both approaches are
somewhat ugly, but the latter is (for me) the lesser of the two evils.
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