#33680: Documentation example of customising model instance loading has a bug
-------------------------------------+-------------------------------------
Reporter: Ali-Toosi | Owner: nobody
Type: Bug | Status: new
Component: Documentation | Version: 4.0
Severity: Normal | Resolution:
Keywords: documentation, | Triage Stage:
from_db, model instance loading | Unreviewed
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Ali-Toosi):
* has_patch: 0 => 1
Old description:
> The docs provide an example of how the model instance loading can be
> changed and how `_loaded_values` can be saved for future comparison here:
> https://docs.djangoproject.com/en/4.0/ref/models/instances/
>
> In this example, it checks if there are any values not loaded from db
> then add them as DEFERRED values so class instantiation would work
> (`cls(*values)`). However, this would mean `values` list has items now
> that do not map to any `field_names` so when at the end of the function,
> we zip them together and store in `_loaded_values`, the code will fail.
>
> The easiest fix for this is to update the `field_names` too so they would
> 1. work and 2. show which fields were not loaded from the db at the time.
New description:
The docs provide an example of how the model instance loading can be
changed and how `_loaded_values` can be saved for future comparison here:
https://docs.djangoproject.com/en/4.0/ref/models/instances/
In this example, it checks if there are any values not loaded from db then
add them as DEFERRED values so class instantiation would work
(`cls(*values)`). However, this would mean `values` list has items now
that do not map to any `field_names` so when at the end of the function,
we zip them together and store in `_loaded_values`, the code will fail.
The easiest fix for this is to update the `field_names` too so they would
1. work and 2. show which fields were not loaded from the db at the time.
I've opened a PR for this here:
https://github.com/django/django/pull/15664
--
--
Ticket URL: <https://code.djangoproject.com/ticket/33680#comment:1>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-updates/0107018093992c44-f6c6b328-5569-4f5c-8c1b-14de6dc12484-000000%40eu-central-1.amazonses.com.
