Find out most derived class in base class

Michal Minich michal.minich at
Fri Nov 19 13:48:50 PST 2010

On Fri, 19 Nov 2010 21:37:45 +0000, div0 wrote:

> On 19/11/2010 21:22, Jonathan M Davis wrote: At runtime, the runtime
> type info for classes forms a DAG.
>>> As D only allows single inheritance it should be trivial to find the
>>> most derived class, though the runtime doesn't currently offer a
>>> function for this.
>> Just because an object is able to know what its actual type is - or
>> even its base classes - does not mean that you could ask it what other
>> types exist which are derived from one of its base types or its exact
>> type. Sure, D definitely _could_ provide the necessary type information
>> at runtime (C# and Java do that sort of thing - which is why thy can
>> have runtime reflection), but it doesn't. At best, you can get
>> information on the types of a particular object from that object, not
>> the types which exist in general.
>> - Jonathan M Davis
> So just ignore the bit about dynamic cast completely then and repeat
> your first incorrect assertion.
> Yes D and C++ do provide a limited amout of runtime type information.
> It's called RTTI surprisingly enough. *cough*
> Dynamic cast, *explicitly* asks at *runtime* if some base class can be
> converted to a *more derived* class.
> You *can not* do that unless base classes know about the classes which
> *inherit from* them.

In current dmd, when you make a cast like: cast (Derived) base, you 
explicitly mentioning the *Derived* type. Its typeinfo contains info 
about classes it derives from, so it the cast just check if type of 
"base" is one of them.

Compiler currently does not push informations from Derived classes to 
base class type info, so it is not possible currently to find out what I 

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