Re: what's a callback?
From: Active8 (reply2group_at_ndbbm.net)
Date: 12/24/04
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Date: Fri, 24 Dec 2004 02:09:05 -0500
On Wed, 22 Dec 2004 06:04:40 GMT, Scott Stephens wrote:
> Active8 wrote:
>
>>>To rephrase Rene's statement: a callback is what you use if a function
>>>'foo' needs to be written now, which has to call another function
>>>'bar' that may not exist yet.
>
>> http://gethelp.devx.com/techtips/cpp_pro/10min/10min0300.asp
>>
>> <quote>
>> A callback function is one that is not invoked explicitly by the
>> programmer; rather the responsibility for its invocation is
>> delegated to another function that receives the callback function's
>> address.
>> </quote>
>>
>> Period.
>>
>>>>Even an empty function is an *implementation* of a function.
>>>
>>>But an empty function is not part of this design --- there's just the
>>>prototype, and a *pointer* to such a function.
>
> Isn't that called an interface? Aren't MS COM objects (such as dhtml
> Active-X objects) an example of such? The COM object interface are
> pointers to an object-specific array of pointers.
In Java, COM, DCOM, OLE, etc., they are called interfaces. In C++,
"prototype" and "function declaration", are synonymous. A function
name without parameters is a pointer, but you can also declare a
variable name for a pointer to a function with a... call it a
special syntax. You knew that, right?
ActiveX really is a good way to write reusable code - DLLs on
steroids. And the remote access (DCOM+/RPC) capability is the balls.
Version control is a positive side benefit of the whole
architecture. It's still a mess - a miracle that MS could pull it
off IMO.
DHTML isn't a COM thing, it's a DOM thing.
-- Best Regards, Mike
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