how can i use the derive-hierarchy at runtime for typechecking?

[Downs]

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Just cast it.
If you have class A { } and class B : A { }
and A foo=new B;
then you can do cast(B) foo and it will be non-null.
On the other hand, if you do A bar=new A;
and you do cast(B) bar, it will be null.

Here's a little utility function for this
void ifIs(S, T)(S obj, void delegate(T) dg) {
  auto casted=cast(T) obj;
  if (casted) dg(casted);
}

Use it like thus

ifIs(foo, (B whee) { /* do stuff with whee */ });

Hope that answers your question.
 --downs/FeepingCreature
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