Re: Reference base class data from derived class?
"John Speth" <johnspeth@yahoo.com> wrote:
Hi group-
I have what is a simple understanding problem with c++. I just can't see a
way to reference the base class data properly in my code. Here's my simple
code that is written in MFC:
// assumed:
class CString {
public:
void Trim();
void TrimLeft();
void TrimRight();
String Left( int ) const;
};
class CStringTrim : public CString
{
void Trim(void)
{
// Strip comments
int n = Find('#');
if(n != -1) *this = Left(n);
// Clean the line
TrimLeft();
TrimRight();
}
};
I simply want to have Trim() discard a string comment (#) and then trim
leading and trailing whitespace and leave the resultant string data in
place. My problem is I don't know how to refer to base class' string value
(see my failed attempt at using "*this").
Why did the attempt fail? I suspect that your attempt didn't work
because CString has a non-virtual Trim function, and you are attempting
to call your Trim on a CString* or reference that actually points to an
object of your class. That doesn't work, because the compiler will call
CString::Trim instead of yours.
Try this instead:
void myTrim( CString& str ) {
int n = str.Find( '#' );
if ( n != -1 )
str = str.Left( n );
str.TrimLeft();
str.TrimRight();
}
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