Re: Data dispatching using dynamic_cast. How to avoid it?

"Alf P. Steinbach" <>
Fri, 14 Mar 2008 07:33:11 +0100
* D. Susman:

On Mar 13, 7:11 pm, Erik Wikstr?m <> wrote:

On 2008-03-13 16:45, D. Susman wrote:

I am working on a data centric project. I have a Process function that
will be called by some thread. The signature goes:
void Process( Base* base )
There are hundred possibilities on what "base" actually (i.e. actual
run-time type) is. I would like to avoid the bulky if statements to
handle the downcasts. Is there a common approach/idiom to handle that?

You want Base to have a process() function so you can do something like

  void Process( Base* base )

And then all you need to do is override the process() function in all
the base-classes.

Erik Wikstr?m

That is not possible since Base objects have been designed as bean
classes due to the used data distribution technology, i.e. classes
holding only data & get/sets (I know this is not good OO but think of
it as a sort of legacy I have deal with)

class IBase
    typedef boost::shared_ptr<IBase> Ptr;

    virtual ~IBase() {}

    virtual void process() = 0;

class SensibleA: virtual IBase
     boost::shared_ptr<BeanA> myData;

     SensibleA( SensibleA const& );
     SensibleA& operator=( SensibleA const& );

     typedef boost::shared_ptr<SensibleA> Ptr;
     explicit SensibleA( BeanA* pData ): myData( pData ) {}

     virtual void process() { ... }

IBase::ptr sensibleFrom( Base* p ) { ... }
// This function might be simplified by using a factory repository
// with factories identified by some bean class id.

void process( IBase::Ptr pBean )

Cheers, & hth.,

- Alf

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