Re: Sub-Classing HTML::Template v2.7

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 = shift;
        my $class = ref($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 ----- 
From: "Cory Trese" <[email protected]>
To: "Cory Trese" <[email protected]>; <[email protected]>
Sent: Saturday, March 05, 2005 4:59 AM
Subject: RE: [htmltmpl] Sub-Classing HTML::Template v2.7


> Hello,
> 
> 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( ).
> 
> 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:
> 
> $loop->[HTML::Template::LOOP::TEMPLATE_HASH]{$starts_at}
> 
>   = HTML::Template->_new_from_loop(
> 
> 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.
> 
> $loop->[HTML::Template::LOOP::TEMPLATE_HASH]{$starts_at}
> 
>   = ref( $self )->_new_from_loop(
> 
> 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.
> 
> However, I do know that making this change caused my sub-classes to
> completely work and I am very happy about that.
> 
> Sincerely,
> Cory Trese
> Lead Web Application Developer
>  
> O'NEIL & ASSOCIATES, INC.
> 495 Byers Rd.
> Miamisburg, Ohio 45342-3662
> Phone: (937) 865-0846 ext. 3038
> Fax: (937) 865-5858
> E-mail: [[email protected]]
> 
> 
> |> -----Original Message-----
> |> From: [email protected] 
> |> [mailto:[email protected]] On 
> |> Behalf Of Cory Trese
> |> Sent: Thursday, March 03, 2005 11:32 AM
> |> To: [email protected]
> |> Subject: [htmltmpl] Sub-Classing HTML::Template v2.7
> |> 
> |> Hello,
> |> 
> |> From some previous traffic on this list, Sam Tregar said:
> |> 
> |> |> Ultimately HTML::Template v2 doesn't offer much in terms 
> |> of official 
> |> |> support for sub-classes and extensions.  That's a 
> |> deficiency I intend 
> |> |> to address in the perpetually-delayed v3.
> |>  
> |> I am trying to create a sub-class of HTML::Template that 
> |> over-rides the 'param( )' method.  The code below "works" -- 
> |> mostly -- but I have a feeling that I'm doing this all 
> |> wrong.  Does anyone have some advice or a link on 
> |> HTML::Template v2 sub-classing?  I looked at 
> |> "HTML::Template::Expr" -- my code below is based, roughly, 
> |> on this module.
> |> 
> |> My major questions are:
> |> 
> |> 1. How does a sub-class of HTML::Template construct itself?  
> |> Should I over-ride 'new( )' or use something like 'make_new( 
> |> )' to wrap 'new( )'
> |> or 'SUPER::new( )'.
> |> 
> |> 2. What packages should my 'param( )' method be overridden 
> |> in?  More than HTML::Template?
> |> 
> |> The thing that doesn't work right:
> |> 
> |> 1. calls to 'param( )' seem to loose my 'i18n_strings' 
> |> object -- it isn't ALWAYS present in 'options' when I call 
> |> 'param( )', just most of the time.  
> |> 
> |> I _think_ that this is somehow related to some of the 
> |> 'param( )' methods I'm using being in the class 'make_new( 
> |> )' returns, and others, constructed somewhere else, but 
> |> still using my 'param( )' method.  I know that's confusing I 
> |> haven't slept much in the past few days, sorry.
> |> 
> |> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> |> package Service::Template;
> |> 
> |> use strict;
> |> use vars qw($VERSION);
> |> 
> |> $VERSION = '0.01';
> |> 
> |> use HTML::Template;
> |> 
> |> use base 'HTML::Template';
> |> 
> |> sub make_new {
> |>   my $pkg = shift;
> |>   my $self;
> |> 
> |>   # check hashworthyness
> |>   croak("Service::Template->new() called with odd number of 
> |> option parameters - should be of the form option => value")
> |>     if (@_ % 2);
> |>   my %options = @_;
> |> 
> |> 
> |>   # create an HTML::Template object, catch the results to keep error
> |>   # message line-numbers helpful.
> |>   eval {
> |>     $self = $pkg->new(%options );
> |>   };
> |>   croak("Service::Template->new() : Error creating 
> |> HTML::Template object
> |> : $@") if $@;
> |> 
> |>     $self->{options}->{i18n_strings} = $options{'i18n_strings'};
> |> 
> |> 
> |>   return $self;
> |> }
> |> 
> |> 1;
> |> 
> |> package HTML::Template;
> |> 
> |> sub param {
> |>  ...
> |> }
> |> 
> |> 1;
> |> 
> |> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> |> 
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