I just finished the tutorial on CPAN a couple of weeks ago. A join is created shortly after your first code sample.

        # Add a record to the join table for this book, mapping to 
        # appropriate author
        $book->add_to_book_authors({author_id => $author_id});
        # Note: Above is a shortcut for this:
        # $book->create_related('book_authors', {author_id => $author_
+id});
        
        # Assign the Book object to the stash for display in the view
        $c->stash->{book} = $book;
[download]

As for your second question. You need to show me what you have in the list subroutine for me to understand what is going on. Your template file is calling 'books/list' which means 'sub list' in Books.pm (you should have created that in the previous tutorial "More Catalyst Basics' In the tutorial on CPAN it looks like this:

     
    sub list : Local {
        # Retrieve the usual Perl OO '$self' for this object. $c is th
+e Catalyst
        # 'Context' that's used to 'glue together' the various compone
+nts
        # that make up the application
        my ($self, $c) = @_;
    
        # Retrieve all of the book records as book model objects and s
+tore in the
        # stash where they can be accessed by the TT template
        $c->stash->{books} = [$c->model('DB::Books')->all];
        
        # Set the TT template to use.  You will almost always want to 
+do this
        # in your action methods (action methods respond to user input
+ in
        # your controllers).
        $c->stash->{template} = 'books/list.tt2';
    }
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If you haven't been there yet you can find all the most updated chapters on CPAN here

Thanks Actualize. Here is the list sub.

sub list : Local {
    # Retrieve the usual Perll OO '$self' for this object. $c is the C
+atalyst
    # 'Context' that's used to 'glue together' the various components
    # that make up the application.
    my ($self, $c) = @_;

    # Retrieve all of the book records as book model objects and store
+ in the
    # stash where they can be accessed by the TT template
    $c->stash->{books} = [$c->model('DB::Books')->all];

    # Set the TT template to use. You will almost always want to do th
+is
    # in your action methods (action methods respond to user input in
    # your controllers).
    $c->stash->{template} = 'books/list.tt2';
}
[download]

Your sub list is exactly the same as it is in the tutorial. After looking over the tutorial and thinking about the error, it looks like the id field for the author is not being passed to the object. There are a few reasons this could happen.

• It could be because you are typing in the wrong url
Here's the right one: http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
• It also could be because there is an error in the code I posted above for joining with the author id:

# Add a record to the join table for this book, mapping to 
# appropriate author
$book->add_to_book_authors({author_id => $author_id});
# Note: Above is a shortcut for this:
# $book->create_related('book_authors', {author_id => $author_id});
# Assign the Book object to the stash for display in the view
$c->stash->{book} = $book;
[download]

• It could be some errors in the DBIx::Class setup from "More Catalyst Basics".
If you happen to leave out a line or write an error in your schema files, your queries may not come out correctly.
-Actualize

I am a Catalyst newbie as well but it seems to me you might not have the database or DBIC schema setup right. I would make sure you have the primary keys properly defined in the tables and that Schema/ files were created (assuming you are using the static schema by now like in the tutorial).

DBIC should increment the primary key for you automatically and you don't need to supply it in create. To find documentation on create() look at ResultSet in DBIx::Class. The $c->model('...') objects inherit from DBIx::Class.

I seem to remember uri_for screwing up on me the same way but I never found out why.

But start at the database, use DBIC_TRACE=1 script/myapp_server.pl or temporarily switch to SQLite like in the tutorial?