How to create dao class with identity column as primary key?

[Sabra Crolleton]

Hi Timo,

I can probably add the identity column stuff to daos this weekend and that
would solve your first issue. I have to admit that I do not use daos (just
sql or s-sql), so they have never been a high priority for me.

With respect to references and foreign keys to other tables, I can also try
to write up an explanation this weekend, but please understand that
postmodern daos are really simple. They are not full ORMs.  Maybe someone
else on the mailing list can write up how they use them.

>From a design standpoint, I agree that I would not include user passwords
in a dao class with the rest of the user information. (I do hope those are
salted passwords as well.) That also implies that passwords should not be
in the same table as the rest of the user information. However, your
password validation function just needs the user id and the password to be
tested. Why pass around an entire user dao? (This shows my biases as a dba
rather than a developer.)

But I am confused by your comment about adding a method to a user dao
class. Common lisp classes do not have methods. Methods are generic and are
specialized on their parameters. So I could write a validate-password
generic function that takes two parameters, a user-id and a password
string. Then I would write two methods, one that accepted an integer as the
user-id parameter and a second method that accepted a user-dao as the
user-id parameter (and then internally extracted the user-id out of the
user dao). See, e.g. the explanations here:
http://www.gigamonkeys.com/book/object-reorientation-generic-functions.html

Sabra

On Tue, Jun 9, 2020 at 4:01 PM Timo Myyrä <timo.myyra at bittivirhe.fi> wrote:

> Hi,
>
> So the best bet would be to just use the create-table to create the
> database
> structure and then define dao classes separately.
> I was trying to avoid that as I'd guess it will be easy to have
> definitions given on
> create-table and dao class to drift apart. I was trying to avoid that by
> using
> just dao so database stuff would be given on just one place.
>
> But now that we're talking daos, how should I handle references to other
> tables
> with dao class? If we take the User dao class for example, I add the users
> table
> and define the user dao. I have then separate passwords table that stores
> user
> passwords. It doesn't feel right to make passwords an dao class. The
> passwords
> are tied very tighly to user so it would seeem logical to query the
> passwords with user
> dao. What would be 'idiomatic way' to do this with postmodern? Just use
> the user dao
> class and add an method to it, which makes normal sql query for users
> passwords?
> Just define password dao and query it with user id?
>
> A bit basic questions. The documents and examples show small cases so its
> hard
> to see the big picture from them.
>
> timo
>
> Sabra Crolleton <sabra.crolleton at gmail.com> writes:
>
> > Hello Timo,
> >
> > A couple of notes here. First "user" is a restricted word for postgresql,
> > so I
> > suggest naming the table "users" instead.
> >
> > Second, your s-sql sample create table misplaced a paren. You need
> another
> > paren after
> > the username column and before the primary key
> >
> > I agree that daos do not yet have identity columns, but that really only
> > prevents you from creating a table using the dao.
> >
> > So consider the following where we create a table using s-sql, insert
> some
> > items,
> > demonstrate that we can retrieve an item using a dao, then demonstrate we
> > can
> > create a dao item, insert it in the table and then retrieve it.
> Postgresql
> > handles all
> > the identity stuff. Also note that I used "users" as the table, but I can
> > create a dao class
> > named "user".
> >
> > (query (:create-table (:if-not-exists 'users)
> >                       ((id :type integer :identity-always t)
> >                        (username :type text))
> >                       (:primary-key id)))
> >
> > (query (:insert-rows-into 'users :columns 'username :values '(("Jason")
> > ("Tim") ("Karolyn"))))
> >
> > (defclass user ()
> >   ((id :col-type integer :accessor id)
> >    (username :col-type text :initarg :username :accessor username))
> >   (:metaclass dao-class)
> >   (:table-name users)
> >   (:keys id))
> >
> > (username (get-dao 'user 1))
> > "Jason"
> >
> > (let ((item (make-instance 'user :username "Zenya")))
> >   (insert-dao item))
> >
> > (username (get-dao 'user 4))
> >
> > "Zenya"
> >
> > Does this help?
> >
> > Sabra Crolleton
> >
> >
> > On Tue, Jun 9, 2020 at 12:41 PM Timo Myyrä <timo.myyra at bittivirhe.fi>
> wrote:
> >
> >> Hi,
> >>
> >> I'm learning to use postmodern as part of my hobby project but I've hit
> a
> >> small bump in the process.
> >> I can have the identity column defined for table without dao with
> >> something like:
> >> (s-sql:sql (:create-table (:if-not-exists 'user)
> >>                   ((id :type int :identity-always t)
> >>                    (username :type text)
> >>                   (:primary-key id)))
> >>
> >> But I intent to use dao classes so it would be nice to have identity
> >> column specified as part to defclass slot options.
> >> Is there some way to create dao class with identity column?
> >>
> >> Br,
> >> Timo M
> >>
> >>
>
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