[Maypole] the subtleties of many-to-many stringification

[Peter Speltz]

--- Seth Gordon <sethg@ropine.com> wrote:

> Work on my Maypolized library database is continuing apace, but I'm 
> confused by a certain detail.
> 
> My database has a "titles" table, an "authors" table, and a 
> "title_author_rel" table linking the two:
> 
> CREATE TABLE title_author_rel (
>      title_id integer,
>      author_id integer,
>      relationship character(6) DEFAULT 'by'::bpchar
>          -- 'by', 'ed.', 'trans.', etc.
> );
> 
> I set up the relationship in my application package...
> 
> package JeevesLibrary;
> #...
> JeevesLibrary::TitleAuthorRel->has_a(title_id => 'JeevesLibrary::Titles');
> JeevesLibrary::TitleAuthorRel->has_a(author_id => 'JeevesLibrary::Authors');
> 
> JeevesLibrary::Titles->has_many(authors =>
>      [ JeevesLibrary::TitleAuthorRel => author_id ]);
> JeevesLibrary::Authors->has_many(titles =>
>      [ JeevesLibrary::TitleAuthorRel => title_id ]);
> 
> 
> ...and everything Just Worked, except for one small detail: the 
> "authors" list on the ...library/titles/view/#### page just has the 
> authors' names, and not the relationships.
> 

Isn't this what you want since you looking at the title already?

> I can make the list show relationships by changing the many-to-many 
> relationship and defining how to stringify title_author_rel:
> 
> package JeevesLibrary;
> #...
> JeevesLibrary::Titles->has_many(authors => 'JeevesLibrary::TitleAuthorRel');
> # ...
> # ...
> package JeevesLibrary::TitleAuthorRel;
> #...
> sub stringify_self {
>      my $self = shift;
>      return $self->relationship . ' ' . $self->author_id;
> }
> 
> This makes the names in the authors list show up a "by Smith" instead of 
> just "Smith", but then the links take me to a title_author_rel/view/### 
> page instead of an author_view/### page.
> 
> I tried adding a view method to JeevesLibrary::TitleAuthorRel that would 
>   look up the appropriate author object and swap it in (an object 
> switcheroo rather than the template switcheroo), but
> When I try to add a "sub view :Exported {}" method to one of my model 
> packages, my module gets a compilation error:
> 
> Couldn't require JeevesLibrary - Invalid CODE attribute: Exported at 
> /home/sethg/bin/JeevesLibrary.pm line 106
> 
> Well, *that*'s damn strange.
> 
> I worked around this by overriding the process method in 
> JeevesLibrary::TitleAuthorRel:
> 
> sub process {
>      my ($class, $r) = @_;
>      my $method = $r->action;
>      return if $r->{template};
>      $r->{template} = $method;
>      $r->objects( [] );
>      my $tar = $class->retrieve($r->{args}->[0]);
>      if ($tar) {
>          my $author = $tar->author_id;
>          $r->objects( [$author] ) if $author;
>      }
>      $r->model_class('JeevesLibrary::Authors');
>      $r->{template_args}{title} =
>          ' author / ' . $r->config->application_name;
>      JeevesLibrary::Authors->$method($r, $author, @{ $r->{args} } );
> }
> 
> This seems to work, but I am still wondering
> 
> (a) why I can't add :Exported methods, dammit

don't know, This used to happen to me happen sometimes. Do you have an
overrident process method in a base model class? I think it was syntax errors
or my overriden process method in my base model class or maybe an upgrade.
Sorry not more helpful.

> (b) if there is a more elegant way to do the same thing
> 

Do the object switcheroo in the view Template instead, maybe or just modify the
template.

Isn't authors an array possibly? I can't see how view template handles that as
it seems to print the column. Does TT2 automatically print all elements of
array? 



=====
pjs


		
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