#30631: Prefixing Q Objects
-------------------------------------+-------------------------------------
Reporter: | Owner: nobody
efficiosoft |
Type: New | Status: new
feature |
Component: Database | Version: 2.2
layer (models, ORM) |
Severity: Normal | Keywords: prefix q objects
Triage Stage: | Has patch: 1
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
I'm currently spending a lot of time on development of a project using
Django and worked out something that I think could be of use for all
Django users.
I added a new `.prefix(prefix)` method to the `Q` object, allowing to
shift pre-built `q` objects to a related field. I think this can change
the way people build managers completely, because instead of methods
returning filtered querysets, one can just return `Q` objects, which can
then be used from related models without repeating the filtering logic.
This is the simple implementation.
```
class Q(django.db.models.Q):
"""
A custom Q implementation that allows prefixing existing Q objects
with some
related field name dynamically.
"""
def prefix(self, prefix):
"""Recursively copies the Q object, prefixing all lookup keys.
The prefix and the existing filter key are delimited by the lookup
separator __.
Use this feature to delegate existing query constraints to a
related field.
"""
return type(self)(
*(
child.prefix(prefix)
if isinstance(child, Q)
else (prefix + LOOKUP_SEP + child[0], child[1])
for child in self.children
),
_connector=self.connector,
_negated=self.negated,
)
```
What do you think, is it worth creating a PR for this functionality? I
haven't written the docs yet, but could write something if you like the
addition.
Best regards
Robert
--
Ticket URL: <https://code.djangoproject.com/ticket/30631>
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