#35641: Pattern matching on model objects
-------------------------------------+-------------------------------------
Reporter: jdahlin | Type: New
| feature
Status: new | Component: Database
| layer (models, ORM)
Version: 5.0 | Severity: Normal
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
It would be nice if I could use pattern matching on Django model fields,
this is especially important in context where I don't know what the model
is, for example in a global post_save() handler where I want to do some
specific logic based on a subclass.
{{{#!python
class Person(Model):
name = TextField(...)
age = IntegerField(...)
class Company(Model):
address = TextField(...)
}}}
I would then be able to do
{{{#!python
@receiver(pre_save)
def pre_save(sender, instance, ....):
# model comes in via signals or some other way, we don't know which
subclass it is
match model:
# equivalent to isinstance(model, Person) and model.age > 10:
case Person(age) if age> 10:
....
# equivalent to isinstance(model, Company) and
model.name.endswith('Street')
case Company(address) if name.endswith('Street'):
....
# or just extract and return a value
case Person(name):
return name
}}}
The implementation for this is fairly straight-forward, add this to
models.Model.
{{{#!python
@property
def __match_args__(self) -> tuple[str, ...]:
return tuple(f.name for f in self._meta.get_fields())
}}}
Happy to create a PR if this is interesting.
--
Ticket URL: <https://code.djangoproject.com/ticket/35641>
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