[storm] problem with many to one relationship

[peter websdell]

James / Jurgen,
Thanks for spotting my silly mistake. Your help is greatly appreciated.

Pete.

2009/9/18 James Henstridge <james at jamesh.id.au>

> On Fri, Sep 18, 2009 at 12:07 AM, peter websdell
> <flyingdeckchair at googlemail.com> wrote:
> > Hello all,
> > Can anyone help me see what I'm doing wrong here?
> >
> > SQL
> > CREATE TABLE IF NOT EXISTS `author` (
> >   `id` int(8) NOT NULL auto_increment,
> >   `first_name` varchar(32) NOT NULL,
> >   `last_name` varchar(32) NOT NULL,
> >   PRIMARY KEY  (`id`)
> > ) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;
> >
> > CREATE TABLE IF NOT EXISTS `book` (
> >   `id` int(8) NOT NULL auto_increment,
> >   `title` varchar(64) NOT NULL,
> >   `author_id` int(8) NOT NULL,
> >   PRIMARY KEY  (`id`)
> > ) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;
> >
> > PYTHON
> > database = create_database("mysql://uname:password@localhost:3306/DB")
> > store = Store(database)
> > class Book(Storm):
> >     __storm_table__ = "book"
> >     id=Int(primary=True)
> >     title = Unicode()
> >     author_id=Int()
> >     author = Reference(author_id,"Author.id")
> >     def __init__(self, title):
> >         self.title = title
> >
> > class Author(Storm):
> >     __storm_table__="author"
> >     id=Int(primary=True)
> >     first_name=Unicode()
> >     last_name=Unicode()
> >     books= ReferenceSet(id,"Book.id")
>
> ^^^ This is the bug.  You've set up your one to many relationship
> between Author's primary key and Book's primary key, rather than with
> Book's foreign key pointing back to Author.  Try changing it to the
> following:
>
>    books = ReferenceSet(id, Book.author_id)
>
> >     def __init__(self, first_name, last_name):
> >         self.first_name = first_name
> >         self.last_name = last_name
> >
> > dog=store.add(Book(u"Dog Called Demolition"))
> > rankin=store.add(Author(u"Robert", u"Rankin"))
> > store.flush()
> > print "rankin id is %i" % (rankin.id)
> > print "dog id is %i" % (dog.id)
> > rankin.books.add(dog)
>
> Due to the above bug, this statement will attempt to set dog.id to
> rankin.id.  dog.author_id remains None, which is why dog.author is
> also None.
>
> > print "rankin book 1 = %s" %(rankin.books.one().title)
> > print "dog author name = %s" % (dog.author.first_name)
> > The error given is:
> > Traceback (most recent call last):
> >   File "models.py", line 33, in <module>
> >     print "dog author name = %s" % (dog.author.first_name)
> > AttributeError: 'NoneType' object has no attribute 'first_name'
> >
> > I thought storm should automatically assign the author_id to the book
> object
> > when the book is added to the Author-object "books" set.
>
> It should.  If it doesn't with the above bug fixed, please tell us.
>
> James.
>
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