Re: a C++ question about union
Ian Collins wrote:
JDT wrote:
NM_UPDOWN
With UDN_DELTAPOS notification handler, MS passes a pointer to NMHDR
which yo can cast to NM_UPDOWN*. With NMHDR (shown below) , you can
use "iDelta" to know the amount it spins while with NMHDR you can
use "code" to know the event type. What I don't understand is why
the same storage (the overlap of the last int and unsigned int) can
provide two different values by casting. Is it not union, is it?
This is a C++ (or even a C) question. If I underhand it, I may
exploit the same tech for my own. Your advise is appreciated. JD
It's not a technique, it's a horrible kludge.
[Mostly directed at the OP]
IOW, there are more reliable ways to do that in C++. However, in C,
since there is no inheritance, relying on certain relationship
between a pointer to a struct member and and the struct object itself
is not completely unheard of. Think "offsetof" macro.
And since we are in a C++ newsgroup, there is probably more merit in
stating what problem you're trying to solve, so that a solution or
two (or three) can be proposed, instead of showing some other solution
to some other problem in an attempt to see if it solves something else
you have not encountered yet...
V
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