on_changeon_change — evaluates an expression when a variable changes value or
quality.
on_change (symbol, s_exp)
symbolAny Gamma symbol.
s_expAny Gamma expression, usually a function or method call.
A list of the following items:
({class_name } fn_name fn_args...)Where fn_name and
fn_args correspond to the
s_exp parameter.
This function causes an expression (s_exp) to be
evaluated when a variable (symbol) changes value or
quality. It can be undone with a call to remove_change.
method AccessData.constructor ()
{
on_change(#$DataSim:Sine,
`(@self).print_point($DataSim:Sine));
after(3, `destroy(@self));
}