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Re: Virtual functions versus callbacks [message #24219 is a reply to message #24218]

Wed, 06 January 2010 11:29

mrjt
Messages: 705
Registered: March 2007
Location: London

Contributor

IMO the difference is that Callbacks are intended for communication between classes/Ctrls and are defined by the Ctrl. Callbacks are usually for actions that imply some sort of state change or contextual (wrong word maybe?) function of the Ctrl.

The virtual methods are the way in which a Ctrl interfaces internally with the underlying GUI/OS and is essentially a cleaner replacement of the message loop. The functions sometimes pass additional information that wouldn't be useful or needed externally.

Example of Callbacks:
WhenAction
WhenAcceptEdit

Example of virtual function:
LeftDown
GotFocus

While there are occasions when the developer might requrie some additional comunication from a Ctrl (ie a Callback) that is the exception rather than the rule in my experience and as demonstrated it is not difficult to add.

I think the current way works very well. Adding Callbacks for all events would just expose a lot of internal message stuff that wouldn't be used very often at the expense of making derived Ctrls more difficult.

IMO obviously, only Mirek could give a definitive answer.

[Updated on: Wed, 06 January 2010 11:38]

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