Just a quick note; dont use $a and $b as named variables.. they're 'special'
(used by the cmp operator) so to avoid ambiguity, use something else/more
descriptive... or use $c if it makes you happy =)
hth
Jos Boumans
----- Original Message -----
From: "Me" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Saturday, June 23, 2001 7:11 PM
Subject: Re: Failed in package programme, how do I use package and object?
> > I'm try my best
>
> And you had 99% of it right.
>
> > package pt;
> > use 5.0000;
> > $a="ok"; #for public using
> > $b="It's";
> >
> > # I don't know why put the newsubroutine in this package,
> > # perhaps, it is a constructer, I copy from PERL's manual,
> > # but it seem don't do anything.
>
> Most of what you wrote is redundant in this
> particular case. You could have written:
>
> package foo;
> sub bar { bless \$qux };
> .
> .
> package waldo;
> $emerson = foo->new;
>
> As you can see, $emerson is just a reference to $qux.
> And $qux is undefined, but has one special property:
> it's been blessed, which is how you turn a reference
> into an object (which is just a reference that knows
> what package it belongs to). Simple, really.
>
> As you start to do more complex things, your constructor
> needs to get a bit more clever.
>
> In particular, what if the following call appears:
>
> oof->new;
>
> and oof ISA (inherits from) foo, and has no constructor
> defined, hence inheriting its constructor from foo?
>
> Well, bless with one argument (as used in my snippet
> above) associates that argument with the current
> package, in the above case, foo, thus constructing a
> foo object not an oof object. So one needs to find out
> what package name was used to call the constructor
> (the package name is conveniently passed as the
> first argument whenever a sub is called using the
> object oriented syntax) and then use the two argument
> form of bless:
>
> > sub new
> > my $type = shift;
> > my $self = {};
> > bless $self,$type;
> > }
>
> The $self = {} bit is so that the object can carry around
> data as well as being blessed (which, applied to a mere
> scalar, means you can only access subs (methods)).
>
> > package main; # My application
> > use pt
> > $c=pt->new();
> > print $c->displaysub().$a;
>
> The $a is assumed to be in the main package.
>
> Use either:
>
> print $c->displaysub().$ct::a;
>
> or use our:
>
> package pt;
> our $a;
> package main;
> print $c->displaysub().$ct::a;
>
> or create displaya, an equivalent of displaysub,
> only for $a, and call it as a class sub:
>
> package pt;
> our $a;
> package main;
> print $c->displaysub().ct->displaya;
>
> hth
>
>
