[vdr] Re: Coding question

[Christian Schuld <chris@sonnengesicht.de>]

Hi,

it not neccessary to use the virtual keyword in sub classes, but it is often 
used as a reminder, that the base function is virtual.

On Thursday 03 June 2004 11:42, Christian Gmeiner wrote:
> Hi Mailingliste,
>
> i have here a question about coding.
>
> Klaus uses abstract (virtual) classes, but why is he also using the virtual
> keyword in this way:
>
> class cDvbDevice : public cDevice {
> private:
>   static bool Probe(const char *FileName);
>          ///< Probes for existing DVB devices.
> public:
>   static bool Initialize(void);
>          ///< Initializes the DVB devices.
>          ///< Must be called before accessing any DVB functions.
>          ///< \return True if any devices are available.
> private:
>   fe_type_t frontendType;
>   int fd_osd, fd_audio, fd_video, fd_dvr, fd_stc;
> protected:
>   virtual void MakePrimaryDevice(bool On);
> public:
>   cDvbDevice(int n);
>   virtual ~cDvbDevice();
>   virtual int ProvidesCa(const cChannel *Channel) const;
>   virtual bool HasDecoder(void) const;
>
> // SPU facilities
>
> private:
>   cDvbSpuDecoder *spuDecoder;
> public:
>   virtual cSpuDecoder *GetSpuDecoder(void);
>
> // Channel facilities
>
> private:
>   cDvbTuner *dvbTuner;
>   void TurnOffLiveMode(void);
> public:
>   virtual bool ProvidesSource(int Source) const;
>   virtual bool ProvidesTransponder(const cChannel *Channel) const;
>   virtual bool ProvidesChannel(const cChannel *Channel, int Priority = -1,
> bool *NeedsDetachReceivers = NULL) const; protected:
>   virtual bool SetChannelDevice(const cChannel *Channel, bool LiveView);
> public:
>   virtual bool HasLock(void);
>
>
> I always thought that i only need to use virtual on the motherclass and the
> childclass dont need it. In my biggest project, a game engine, i dont use
> virtual in the childclass. Could somebody explain this to me?
>
> Thanks, Christian

-- 
Viele Grüße
Christian