Re: dynamic_cast is only casting right?
On 6/3/2010 10:17 PM, A wrote:
[..]
Well, even though there is a chance that dynamic cast can fail in this
example chance is probably next to none.
I will of course handle exception but in more complete version I use it to
cast TObject *Sender into TEdit * so I can use same event for all Edit boxes
to handle the same thing based on *Sender. In particular checking if any of
Edit boxes changed so that Apply button is enabled. So TEdit is descendant
of TObject.
So for example:
void Image_AssignImage(TObject *Sender)
{
try
{
TEdit *dEdit = dynamic_cast<TEdit *>(Sender);
if (dEdit->Modified) ButtonApply->Enabled=true;
}
catch (Exception&e)
{
// do something with exception
}
}
A dynamic_cast to a pointer fails by producing a null pointer, not an
exception. In your case I'd write
void Image_AssignImage(TObject *Sender)
{
if (TEdit *dEdit = dynamic_cast<TEdit*>(Sender))
{
if (dEdit->Modified) ButtonApply->Enbled = true;
}
else // the Sender is not a TEdit
{
// do something
}
}
If you don't check 'dEdit' on being null, the program has undefined
behavior when you use (dereference) dEdit, and in Windows a special
system exception is thrown, not a standard C++ one. Is that what you're
trying to handle? Probably easier and faster without 'try' in your case
here.
V
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