last insert id

[Mathieu Blondel]

Hi,

I'm a new comer to Django so please forgive me if the following has
already a solution.

When one saves an object with the save() method, a common need is to
get the id corresponding to the row that has just been inserted.

p = polls.Poll(...)
p.save()
p.id # is set to None

So here are two possible solutions,
1) Either update the primary key columns from a row when save() is
called
2) Or implement a reload() method which would update the whole object
variables

Thanks for the great work achieved with Django,
Mathieu

[apr...@gmail.com]

Strange, for me it works like said in 1). After the new object is
saved, the id field is not None, but the true id of the object in
database. Maybe I did not understand something?

Also, if you look at the tutorial at
http://www.djangoproject.com/documentation/tutorial1/ it says:

# No polls are in the system yet.
>>> polls.get_list()
[]

# Create a new Poll.
>>> from datetime import datetime
>>> p = polls.Poll(question="What's up?", pub_date=datetime.now())

# Save the object into the database. You have to call save()
explicitly.
>>> p.save()

# Now it has an ID. Note that this might say "1L" instead of "1",
depending
# on which database you're using. That's no biggie; it just means your
# database backend prefers to return integers as Python long integer
# objects.
>>> p.id
1

[Adrian Holovaty]

On 4/18/06, Mathieu Blondel <mblo...@gmail.com> wrote:
> When one saves an object with the save() method, a common need is to
> get the id corresponding to the row that has just been inserted.
>
> p = polls.Poll(...)
> p.save()
> p.id # is set to None
>
> So here are two possible solutions,
> 1) Either update the primary key columns from a row when save() is
> called
> 2) Or implement a reload() method which would update the whole object
> variables

Hi Mathieu,

Django currently does exactly what you described in "1" -- when you
call save() for the first time, the primary key attribute of the
object is updated with the ID of the newly-saved record. This assumes
that field is defined as an AutoField in the model.

Adrian

--
Adrian Holovaty
holovaty.com | djangoproject.com