Oh, you did not declare the types as `ref`. Polymorphism does not work with
plain objects because there is no place to store the virtual tables. Try this:
type Uno = ref object of RootObj
x: float
type Due = ref object of Uno
type Tre = ref object of Uno
y: float
proc newDue(x: float): Due = Due(x: x)
proc newTre(x, y: float): Tre = Tre(x: x, y:y)
method `$`(x: Uno): string {.base.} =
system.`$`(x[])
method `$`(x: Due): string =
system.`$`(x[])
method `$`(x: Tre): string =
system.`$`(x[])
var appo = 1.2
var caz = (if appo>1: newTre(0.5, 2.0) else: newDue(1.0))
echo caz
Run
