isa()typedef x::ref<buttonObj> button; typedef x::ref<windowObj> window; bool is_a_button(const window &w) { return w->isa<button>(); }
The isa() x::obj
method takes an x::ref or an x::ptr template parameter, and returns true if
an x::ref or an x::ptr to this object is capable of getting dynamically casted
to the template x::ref or an x::ptr.
This is equivalent to “dynamic_cast<buttonObj *>(&*w)”, but with a clean syntax.