package Employee4;
##
## An example of inheritance with both some further methods defined for the derived class
## and overridden methods demonstrating polymorphism.
## See testemp3.pl .
use Person5;  ## load this class
@ISA = ("Person5"); ## inherit the class methods as needed.

use Carp;
my $Debugging = 0; ## global in Employee3 ...

## need to initialise the new fields provided by this class
sub new {
  my $class = shift;
  my $self = $class->SUPER::new();
  $self->{SALARY} = undef;
  $self->{ID} = undef;
  $self->{START_DATE};
  return $self;
}

## Unique Employee methods
sub salary {
  my $self = shift;
  if (@_) { $self->{SALARY} = shift }
  return $self->{SALARY};
}

sub id_number {
  my $self = shift;
  if (@_) { $self->{ID} = shift }
  return $self->{ID};
}

sub start_date {
  my $self = shift;
  if (@_) { $self->{START_DATE} = shift }
  return $self->{START_DATE};
}

## Overridden methods - polymorphism
## This completely overrides Person5->peers.
sub peers {
  my $self = shift;
  if (@_) { @{$self->{PEERS}} = @_; }
  return map { "PEON=\U$_" } @{ $self->{PEERS} };
}

## subclass/superclass
sub debug {
  my $self = shift;
  confess "usage: thing->debug(level)" unless @_ = 1;
  my $level = shift;
  if (ref($self)) {
    $self->{_DEBUG} = $level;
  } else {
    $Debugging = $level;
  }
  $self->SUPER::debug($Debugging);
}
1;