No offense, but I may be asking a strange question. I am a beginner, learning advanced OOP, and confused about a few concepts. Coming to the point. It may be ridiculous. But can someone tell me exactly and correctly what does callback literary mean? And how it differs from a proxy class in C++ which we use for information hiding. Apologies in advance, if I missused the terminology.
Asked
Active
Viewed 560 times
2 Answers
0
The idea of a call back is to start some action then do something else until the action completes.
An example from the real world is to telephone the plumber for a repair. The plumber says they are currently at a work site and unable to see their schedule for the next day right now. However the plumber says that they will be in the office later and will be able to check their schedule. The plumber then promises to give you a call back once they are in the office and able to check the schedule. You could then either sit down next to the telephone and wait for the return telephone call (blocking call back) or read a book or paint the house until the plumber calls back (deferred call back).
In C, a callback function is a function body that is specified as a callback. The address of the function, a function pointer, is provided to the function being called to perform some kind of action. When the action is completed the callback function is invoked to do something, usually some form of cleanup and/or notification.
Normally a callback is used when a function is called to start some action and then returns immediately to the caller before the action completes and its result is known. The callback is used as a way to notify the result of the action when the started action is completed.
Another form of callback is to register a function for an event so that when the event happens, the function will be called to do something. So you might specify a callback for when a mouse click event is received.
A proxy class is a class that acts as an interface for a class. You could think of a proxy class as being similar to a stunt double who does the dangerous things for an actor. Or a proxy for a share holder's meeting is a person or organization who stands in for the actual share holder to perform specific duties for the share holder.
A callback is not a proxy though a callback may be used by a proxy as part of the functionality required to do its proxy duties.
Richard Chambers
- 16,643
- 4
- 81
- 106
0
From Wikipedia:
A callback is a reference to executable code, or a piece of executable code, that is passed as an argument to other code.
As for proxy classes, see this question.
It's two different things. An instance of a proxy class can be used as callback, but that's about the only relation I can see between them.
Community
- 1
- 1
Laurent Pireyn
- 6,735
- 1
- 29
- 39