Rails - May 2007 - question about find_by

hi,

i am new to ruby/rails, and i am struggling with the find_by method.
Heres some background on what i am trying to get done:

I have a User object, and a Book. User has_one Book, and Book
belongs_to User.

basically, i have a combo box which displays all the books, i get the
id the book is stored in, from the form and then in the user model
class, i try and find the according and assign the according book,
with this find method:

self.book = Book.find_by_id(b_id)

unfortunately i end up with this error:

Mysql::Error: #42S22Unknown column ''books.user_id'' in
''where clause'':
SELECT * FROM books WHERE (books.user_id = 1)  LIMIT 1

I dont understand why it is searching the user_id column (which doesnt
exist), rather than id ....

At first, i thought something was wrong with my Book.find_by
statement, but i tried the same line in an ActionMailer, and it worked
fine.

can someone please clear this up?

thanks!


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My guess is that it''s because you are using self in the User class.

Try:

@book = Book.find_by_id(b_id)

On May 6, 7:21 pm, "gmon...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org"
<gmon...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> hi,
>
> i am new to ruby/rails, and i am struggling with the find_by method.
> Heres some background on what i am trying to get done:
>
> I have a User object, and a Book. User has_one Book, and Book
> belongs_to User.
>
> basically, i have a combo box which displays all the books, i get the
> id the book is stored in, from the form and then in the user model
> class, i try and find the according and assign the according book,
> with this find method:
>
> self.book = Book.find_by_id(b_id)
>
> unfortunately i end up with this error:
>
> Mysql::Error: #42S22Unknown column ''books.user_id'' in
''where clause'':
> SELECT * FROM books WHERE (books.user_id = 1)  LIMIT 1
>
> I dont understand why it is searching the user_id column (which doesnt
> exist), rather than id ....
>
> At first, i thought something was wrong with my Book.find_by
> statement, but i tried the same line in an ActionMailer, and it worked
> fine.
>
> can someone please clear this up?
>
> thanks!

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My guess is that the associations are set up wrong. If a User has_one
Book then it will indeed assume there''s a user_id column on books. It
may seem slightly unintuitive, but you may want to swap it around - a
User belongs_to a Book, if you have a book_id column on the users
table, and a Book has_one (or has_many) User(s).

On 5/6/07, nathan.powell-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
<nathan.powell-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> My guess is that it''s because you are using self in the User
class.
>
> Try:
>
> @book = Book.find_by_id(b_id)
>
> On May 6, 7:21 pm,
"gmon...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org"
<gmon...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > hi,
> >
> > i am new to ruby/rails, and i am struggling with the find_by method.
> > Heres some background on what i am trying to get done:
> >
> > I have a User object, and a Book. User has_one Book, and Book
> > belongs_to User.
> >
> > basically, i have a combo box which displays all the books, i get the
> > id the book is stored in, from the form and then in the user model
> > class, i try and find the according and assign the according book,
> > with this find method:
> >
> > self.book = Book.find_by_id(b_id)
> >
> > unfortunately i end up with this error:
> >
> > Mysql::Error: #42S22Unknown column ''books.user_id''
in ''where clause'':
> > SELECT * FROM books WHERE (books.user_id = 1)  LIMIT 1
> >
> > I dont understand why it is searching the user_id column (which doesnt
> > exist), rather than id ....
> >
> > At first, i thought something was wrong with my Book.find_by
> > statement, but i tried the same line in an ActionMailer, and it worked
> > fine.
> >
> > can someone please clear this up?
> >
> > thanks!
>
>
> >
>
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Hi Gabriel,

you guessed right...that was my mistake...it does seem counter
intuitive, but my user has the book id, and my books do not has a
user_id, since a book can belong to many users.

but it still isnt working, this line seems to fail in my rhtml file:

Book: <%= current_user.book %>

can i not access relationships this way?


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Unless you''ve defined a to_s method on Book, you want to call the
explicit attribute you wish to display the value of - like
current_user.book.name or current_user.book.title for example.

On 5/6/07, gmoniey-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
<gmoniey-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> Hi Gabriel,
>
> you guessed right...that was my mistake...it does seem counter
> intuitive, but my user has the book id, and my books do not has a
> user_id, since a book can belong to many users.
>
> but it still isnt working, this line seems to fail in my rhtml file:
>
> Book: <%= current_user.book %>
>
> can i not access relationships this way?
>
>
> >
>
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i actually copied the wrong thing. i originally had what you
suggested, but it was failing...after snoopin around a bit...i
realized i accidentally deleted the ''end'' at the end of my
Book
class....stupid vi....

thanks!


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