RE: [Boost-users] Need a method to compare types of data objects atruntime

From: Delfin Rojas (drojas_at_[hidden])
Date: 2005-04-26 15:05:32

It seems Gas_Pedal and Brake_Pedal should not share the same base class. Any
reasons why you want to do this? 

-delfin

> -----Original Message-----
> From: boost-users-bounces_at_[hidden] [mailto:boost-users-
> bounces_at_[hidden]] On Behalf Of Stephen Torri
> Sent: Sunday, April 24, 2005 11:46 AM
> To: boost
> Subject: [Boost-users] Need a method to compare types of data objects
> atruntime
> 
> If I have a abstract class with two classes that implement it how can I
> make a check that tests for the type of the implementation classes?
> 
> For example:
> 
>         class Base {
>         public:
>         	virtual void run (){}
>         	virtual void stop (){}
>         };
> 
>         class Gas_Pedal : public Base {
>         public:
>         	virtual void run (){}
>         	void set_rate (unsigned int);
>         private:
>         	unsigned int m_rate;
>         };
> 
>         class Brake_Pedal : public Base {
>         public:
>         	virtual void stop (){}
>         	void set_pressure (unsigned int);
>         private:
>         	unsigned int m_pressure;
>         };
> 
> When I have a client that receives a Base object I want to be able to
> check at run-time. So that if I am expecting a Gas_Pedal object and I
> receive something else I can perform some recovery action. The software
> I am designing contains an untold number of arrangements of items. Each
> item expect a distinctive input type. If it receives something that it
> does not know how to handle or need I want to throw an error.
> 
> In order to do this I would like to do something like:
> 
>         void process (Base* sobj)
>         {
>         	if (! (isExpectedType(sobj))
>         	{
>         		throw NotForMeException ();
>         	}
> 
>         	Brake_Pedal* bp = dynamic_cast<Brake_Pedal>(sobj);
>         	bp.set_pressure (50);
>         }
> 
> So perhaps my design is flawed that I am running into this situation. I
> am attempting to keep the interface for the Base class simple. The
> underlying types could have different data and access methods because
> they differ so widely in what they will do. This example was given to
> keep things simple.
> 
> Stephen
> 
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