Challenge 2: A Custom Exception — Solution

class InvalidAgeError < StandardError
  def initialize(msg = "Age must be between 0 and 130")
    super
  end
end

def set_age(age)
  raise InvalidAgeError if age < 0 || age > 130

  age
end

begin
  set_age(-5)
rescue InvalidAgeError => e
  puts e.message
end

begin
  puts set_age(33)
rescue InvalidAgeError => e
  puts e.message
end

=begin
Output:
Age must be between 0 and 130
33

Notes:
- InvalidAgeError < StandardError makes this a proper custom exception
  class, following the chapter's rule to inherit from StandardError, not
  the bare Exception class.
- initialize(msg = "...") followed by super passes the default message up
  to StandardError's own initialize, so e.message returns it automatically
  when no custom message is given at the raise site.
- The first begin/rescue block catches the invalid age (-5) and prints the
  custom message. The second begin/rescue block passes a valid age (33)
  through set_age with no exception raised at all, so rescue never
  triggers there and 33 is simply returned and printed.
=end