On Monday, 28 November 2016 at 14:35:36 UTC, Namespace wrote:
We have a handy dandy syntax for this:
if (MyClassInt subclass = cast(MyClassInt)value) {
writeln(subclass.value);
}
If it doesn't cast to said type (it will be null) that branch
won't execute.
Just out of interest: it looks like a dynamic_cast in C++ which
is considered as slow operation. Is that D cast also a dynamic
cast and also slow? I've never used it, so I'm a bit curious.
The cast from a class type to a sub class in itself does
absolutely nothing. It has only an effect when you call a virtual
method. This is slow because of the indirection that happens when
the right offset has to be found in the VTBL.
