Opened 3 months ago
Last modified 3 months ago
#35641 closed New feature
Pattern matching on model objects — at Initial Version
Reported by: | Johan Dahlin | Owned by: | |
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Component: | Database layer (models, ORM) | Version: | 5.0 |
Severity: | Normal | Keywords: | |
Cc: | Johan Dahlin | Triage Stage: | Unreviewed |
Has patch: | no | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description
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.
class Person(Model): name = TextField(...) age = IntegerField(...) class Company(Model): address = TextField(...)
I would then be able to do
@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.
@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.
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