[ale] OOP in perl

[Christopher Fowler]

Here is the example from the Perl book with some of my mods:


package RegularEmployee;

sub new {
    shift;
    my ($name, $age, $starting_position, $monthly_salary) = @_;
    my $r_employee = {
        "name"           => $name,
        "age"            => $age,
        "position"       => $starting_position,
        "monthly_salary" => $monthly_salary,
        "months_worked"  => 0,
    };

    bless $r_employee, 'RegularEmployee';   # Tag object with pkg name
    return $r_employee;                     # Return object
}
sub promote {
#...
}

sub monthsWorked {
   my $r_emp = shift;
   (my $v1) = @_;
   $r_emp->{'months_worked'} = $v1;
   return;
}
sub compute_ytd_income{
   my $r_emp = shift;
   return $r_emp->{'monthly_salary'} * $r_emp->{'months_worked'};
}

return 1;


My question is since I got 2 different responses of different ways to do
this, which is the best?  Is the example above a good or bad way to go? 
I do not want to switch standard mid-stream.

Thanks,
Chris

On Fri, 2003-04-25 at 09:42, Fletch wrote:
> >>>>> "Christopher" == Christopher Fowler <cfowler at outpostsentinel.com> writes:
> 
> [...]
> 
>     > my %addr = { 'Name' => "",
> 
> You mean either `my %addr = ( ... )' or `my $addr = { }'.  This should
> have griped about assigning an odd number of items to a hash (since a
> hashref is only a single scalar value).
> 
> 
>     >    bless \%addr, 'Address';
>     >    return %addr;
> 
> Perl objects are blessed references.  You return the hash itself
> (which gets flattened out into a list of key value pairs), and the
> blessed hash disappears when the scope ends.  You really want
> something more along these lines:
> 
> 
> sub new {
>   my $class = shift;
>   my $self = { ... };
> 
>   return bless $self, $class
> }
> 
> 
> If you want to be able to call new() on existing instances you may
> want to add in `$class = ref($class) || $class;' in there somewhere,
> but that's not required (even though lots of people cargo cult it into
> everything (even I'm guilty of that :)).
> 
> 
> 
>     > # If I do not place a return 1 at the end, I get the 
>     > # following error
>     > #Address.pm did not return a true value at ./test line 4.
>     > #BEGIN failed--compilation aborted at ./test line 3.
> 
> Erm, yes.  Perl requires modules to return a true value to indicate
> they've successfully loaded.  See perldoc perlmod.
> 
> 
>     > my $addr = Address::new(); $addr->test();
> 
> You mean `Address->new()'.  `Address::new()' is just invoking a sub
> using its fully qualified name.  Not that it matters in this case
> because your new() ignores what it was called on, but for future
> reference.
> 
> 
>     > --- Execution --- [cfowler at cfowler OOP]$ perl test 
>     > Can't call method "test" without a package or object reference at test line 7.
>     >  [cfowler at cfowler OOP]$
> 
> This is because $addr doesn't contain a blessed reference (see first
> comment).
> 
> 
> Back to the documentation mines with you! :)
> 
> 
> perlreftut          Perl references short introduction
> perlboot            Perl OO tutorial for beginners
> perltoot            Perl OO tutorial, part 1
> perltooc            Perl OO tutorial, part 2
> perlbot             Perl OO tricks and examples
> 
> 
> See also _Object Oriented Perl_ by Damian Conway.  If you have one
> other perl book besides the Camel and the cookbook, it should be OOP.
> 
> 
> -- 
> Fletch                | "If you find my answers frightening,       __`'/|
> fletch at phydeaux.org   |  Vincent, you should cease askin'          \ o.O'
> 770 294-0820 (m)      |  scary questions." -- Jules                =(___)=
>                       |                                               U
> _______________________________________________
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