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[vdr] Re: Coding question
> 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
I do it this way because I want to see immediately when looking at
a child class which functions are virtual.
IMHO it was a mistake of Bjarne Stroustrup to allow the 'virtual'
keyword to be left out in child classes.
Klaus
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