Re: [htmltmpl] Sub-Classing HTML::Template v2.7
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Re: [htmltmpl] Sub-Classing HTML::Template v2.7
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From: Mathew R. <mat...@re...> - 2005-03-06 23:49:09
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There are some places in H::T where this is done... and I agree with =
you -> its wrong if you need to subclass H::T...
However, you should be able to simply change it to:
$self->_new_from_loop(...)
Perl will automatically dereference $self so as to determine the correct =
package name - in fact ref($self) may return a string which is not =
appropriate, in certain scenarios (eg: it may return HTML::Template when =
it should return, say, MyHtmlTemplate). Then _new_from_loop should =
implement:
sub _new_from_loop {
my $proto =3D shift;
my $class =3D ref($proto) || $proto;
...
}
at this point $class will contain the correct package name.
The same point could be said about H::T::E::output(), since it does =
this:
sub output {
....
HTML::Template::output(...)
...
}
which again is incorrect if H::T::E is to be subclass'able.
FWIW, the version of H::T that I have modified (available at: =
http://members.optusnet.com.au/~mathew ) also makes this mistake in some =
of the code that I have extended... ie we are all fallable...
regards,
Mathew
----- Original Message -----=20
From: "Cory Trese" <Ct...@on...>
To: "Cory Trese" <Ct...@on...>; =
<htm...@li...>
Sent: Saturday, March 05, 2005 4:59 AM
Subject: RE: [htmltmpl] Sub-Classing HTML::Template v2.7
> Hello,
>=20
> I have found the root of my problem! All the code below was centered
> around trying, and failing, to fully replace all instances of the
> HTML::Template 'param( )' method within our code-base. I thought that
> by building a sub-class and overriding param, I would be able to
> accomplish this. However, I was unable to override all calls to =
'param(
> )' -- some within HTML::Template remained using the SUPER::param( ).
>=20
> I attempted to overwrite the package method, as seen below. This,
> however, doesn't actually work. So again, no dice. Until I found the
> following code in HTML::Template around Line #2112:
>=20
> $loop->[HTML::Template::LOOP::TEMPLATE_HASH]{$starts_at}
>=20
> =3D HTML::Template->_new_from_loop(
>=20
> This does not seem friendly to sub-classes ... I didn't see any
> references to this type of issue in Damian Conway's Object Oriented =
Perl
> book, but I found a solution that works great for my sub-classes.
>=20
> $loop->[HTML::Template::LOOP::TEMPLATE_HASH]{$starts_at}
>=20
> =3D ref( $self )->_new_from_loop(
>=20
> This way, the "_new_from_loop" call always occurs against the correct
> class -- HTML::Template or otherwise. I have no production code to =
test
> compatibility with HTML::Template::Expr so I cannot state if this type
> of change will work for everyone trying to sub-class HTML::Template.
>=20
> However, I do know that making this change caused my sub-classes to
> completely work and I am very happy about that.
>=20
> Sincerely,
> Cory Trese
> Lead Web Application Developer
> =20
> O'NEIL & ASSOCIATES, INC.
> 495 Byers Rd.
> Miamisburg, Ohio 45342-3662
> Phone: (937) 865-0846 ext. 3038
> Fax: (937) 865-5858
> E-mail: [ct...@on...]
>=20
>=20
> |> -----Original Message-----
> |> From: htm...@li...=20
> |> [mailto:htm...@li...] On=20
> |> Behalf Of Cory Trese
> |> Sent: Thursday, March 03, 2005 11:32 AM
> |> To: htm...@li...
> |> Subject: [htmltmpl] Sub-Classing HTML::Template v2.7
> |>=20
> |> Hello,
> |>=20
> |> From some previous traffic on this list, Sam Tregar said:
> |>=20
> |> |> Ultimately HTML::Template v2 doesn't offer much in terms=20
> |> of official=20
> |> |> support for sub-classes and extensions. That's a=20
> |> deficiency I intend=20
> |> |> to address in the perpetually-delayed v3.
> |> =20
> |> I am trying to create a sub-class of HTML::Template that=20
> |> over-rides the 'param( )' method. The code below "works" --=20
> |> mostly -- but I have a feeling that I'm doing this all=20
> |> wrong. Does anyone have some advice or a link on=20
> |> HTML::Template v2 sub-classing? I looked at=20
> |> "HTML::Template::Expr" -- my code below is based, roughly,=20
> |> on this module.
> |>=20
> |> My major questions are:
> |>=20
> |> 1. How does a sub-class of HTML::Template construct itself? =20
> |> Should I over-ride 'new( )' or use something like 'make_new(=20
> |> )' to wrap 'new( )'
> |> or 'SUPER::new( )'.
> |>=20
> |> 2. What packages should my 'param( )' method be overridden=20
> |> in? More than HTML::Template?
> |>=20
> |> The thing that doesn't work right:
> |>=20
> |> 1. calls to 'param( )' seem to loose my 'i18n_strings'=20
> |> object -- it isn't ALWAYS present in 'options' when I call=20
> |> 'param( )', just most of the time. =20
> |>=20
> |> I _think_ that this is somehow related to some of the=20
> |> 'param( )' methods I'm using being in the class 'make_new(=20
> |> )' returns, and others, constructed somewhere else, but=20
> |> still using my 'param( )' method. I know that's confusing I=20
> |> haven't slept much in the past few days, sorry.
> |>=20
> |> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> |> package Service::Template;
> |>=20
> |> use strict;
> |> use vars qw($VERSION);
> |>=20
> |> $VERSION =3D '0.01';
> |>=20
> |> use HTML::Template;
> |>=20
> |> use base 'HTML::Template';
> |>=20
> |> sub make_new {
> |> my $pkg =3D shift;
> |> my $self;
> |>=20
> |> # check hashworthyness
> |> croak("Service::Template->new() called with odd number of=20
> |> option parameters - should be of the form option =3D> value")
> |> if (@_ % 2);
> |> my %options =3D @_;
> |>=20
> |>=20
> |> # create an HTML::Template object, catch the results to keep =
error
> |> # message line-numbers helpful.
> |> eval {
> |> $self =3D $pkg->new(%options );
> |> };
> |> croak("Service::Template->new() : Error creating=20
> |> HTML::Template object
> |> : $@") if $@;
> |>=20
> |> $self->{options}->{i18n_strings} =3D $options{'i18n_strings'};
> |>=20
> |>=20
> |> return $self;
> |> }
> |>=20
> |> 1;
> |>=20
> |> package HTML::Template;
> |>=20
> |> sub param {
> |> ...
> |> }
> |>=20
> |> 1;
> |>=20
> |> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> |>=20
> |> *************************************************************
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> |>=20
>=20
> **********************************************************************
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you have
> received this communication in error, please contact the sender at =
O'Neil &
> Associates, Inc., immediately. Any copying, dissemination, or =
distribution
> of this communication, other than by the intended recipient, is =
strictly
> prohibited.
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>=20
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>=20
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