Slots can be used for receiving indicators, but they're additionally normal member functions.
The alerts and slots mechanism is a central characteristic of Qt and doubtless the half that differs most from the features provided by other frameworks. While successful frameworks utilizing this technique do exist, callbacks might be unintuitive and should undergo from issues in guaranteeing the type-correctness of callback arguments.
In Qt, we now have another to the callback technique: We use indicators and slots. The processing perform then calls the callback when appropriate. While ten non-virtual perform calls could sound like so much, it's much much less overhead than any new or delete operation, for example.
Basically, emitting a signal that's related to some slots, is approximately ten instances slower than calling the receivers instantly, with non-virtual function calls. That is the overhead required to find the connection object, to safely iterate over all connections (i.e.
checking that subsequent receivers haven't been destroyed during the emission), and to marshall any parameters in a generic trend. Qt's signals and slots mechanism ensures that for those who connect a sign to a slot, the slot can be called with the sign's parameters at the correct time.
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