Assign_new and embed_templates

How do you use assign_new with an embedded template

is is possible ?

since this construct does not leave possibility to put assign_new before H~

embed_templates "comps/*"

attr :val, :string
attr :other, :any, default: fun(val) ??? 
def show(assigns)

otherwise is it possible in the attr line to compute a defautl value based on functions of other attrs ?

or you must not embed the template if assigns needs to be complemented with computed values ?