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From: Marcin Tustin (mt_at_[hidden])
Date: 2005-04-25 04:29:10


const type_info& type = typeid(*v); Comparable based on string
representation. Part of standard. Header <typeinfo>.

> -----Original Message-----
> From: Stephen Torri [mailto:storri_at_[hidden]]
> Sent: 24 April 2005 19:46
> 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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