deriving a class from Ostream

[hitech_guy]

Hi,

I am creating my own class derving from ostream. I am facing problem in
compiling with GNU G++ compiler under linux
class IWCoreEXPORT IWAFTraceLine : public ostream
{
public:
IWAFTraceLine( const char* pszFileName = 0,int
nLine = 0, const char* pszLayer = 0,int nError = -1 );
~IWAFTraceLine( );

IWAFTraceLine( const IWAFTraceLine& that );
IWAFTraceLine& operator = ( const IWAFTraceLine& that );
ostream buffer;

//!!! These numbers can't be negative, so why not uint or size_t?
int getErrorNumber( ) const;
void setErrorNumber( int nError );

int getLineNumber( ) const;
void setLineNumber( int nLine );

const String& getFileName( ) const;
void setFileName( const String& strFileName );

const String& getLayer( ) const;
void setLayer( const String& strLayer );

String getMessage( ) const;

Boolean existsSubstInfo( const String& key ) const;
const String& findSubstInfo( const String& key ) const;
void insertSubstInfo( const String& key,
const String& value );
private:
typedef map< String, String, less < String > ,allocator<String>

SubstInfoMap ;

private:
String m_strFileName;
int m_nLine;
int m_nError;
String m_strLayer;
SubstInfoMap m_substInfo;
strstreambuf m_msg;
};
//!!! Should this be nested within IWAFException??
typedef vector< IWAFTraceLine ,allocator <IWAFTraceLine> >
IWAFTraceLines;

/************************************************** ******/
IWAFTraceLine::IWAFTraceLine( const char* pszFileName, int nLine,
const char* pszLayer,int nError) : m_strFileName.c_str(),
m_nLine,m_strLayer.c_str(),m_nError

{
if(pszFileName)
m_strFileName = pszFileName;

if(pszLayer)
m_strLayer = pszLayer;

init(&m_msg);
}

Can you please tell me that why the code is not been compiled in the
Linux with GNU G++ compiler.

mail me at di*************@hitechclub.com

regards
dinesh

[Ron Natalie]

hitech_guy wrote:

Hi,

I am creating my own class derving from ostream. I am facing problem in
compiling with GNU G++ compiler under linux
When you are asking for free advice on the net, it's best to give a full
description of what you observed and what you were expecting. What
errors did you receive?


IWAFTraceLine( const IWAFTraceLine& that );
IWAFTraceLine& operator = ( const IWAFTraceLine& that );
ostream does not have copy construction/assignment semantics. You can't
implement anything that would attempt to copy/assign an ostream or
anything containing or derived from it. This is why streams are dealt
with by reference most places.
ostream buffer;

Unless your stream wrapper does little more than wrap the constructor of
a stream, you probably want to investigate writing a custom stream
buffer. The problem is that lots of the functions/operators that take
ostreams will end up taking your IWAFTraceLine and downcasting it to a
ostream& and you'll lose the stuff you added in the derived class.