def datastream(cls):
"""
Class decorator to track model changes to datastream
Usage
@datastream
class MyModel(Model):
...
def iter_changed_datastream(self, changed_fields=None):
yield <datastream name>, <object id>
...
yield <datastream name>, <object id>
"""
if hasattr(cls, "iter_changed_datastream"):
if is_document(cls):
mongo_signals.post_save.connect(_on_document_change, sender=cls)
mongo_signals.pre_delete.connect(_on_document_change, sender=cls)
else:
django_signals.post_save.connect(_on_model_change, sender=cls)
django_signals.pre_delete.connect(_on_model_change, sender=cls)
return cls
def model(cls, m_cls):
"""
Decorator to denote models with labels.
Contains field validation and `effective_labels` generation.
Usage:
```
@Label.model
class MyModel(...)
```
Adds pre-save hook to check and process `.labels` fields. Raises ValueError
if any of the labels is not exists.
Target model may have `iter_effective_labels` method with following signature:
```
def iter_effective_labels(self) -> Iterable[List[str]]
```
which may yield a list of effective labels from related objects to form
`effective_labels` field.
:param m_cls: Target model class
:return:
"""
def default_iter_effective_labels(instance) -> Iterable[List[str]]:
yield instance.labels or []
def on_pre_save(sender, instance=None, document=None, *args, **kwargs):
instance = instance or document
# Clean up labels
labels = Label.merge_labels(
default_iter_effective_labels(instance))
instance.labels = labels
# Build and clean up effective labels
can_expose_label = getattr(sender, "can_expose_label",
lambda x: True)
labels_iter = getattr(sender, "iter_effective_labels",
default_iter_effective_labels)
instance.effective_labels = [
ll.name for ll in Label.objects.filter(
name__in=Label.merge_labels(labels_iter(instance)))
if can_expose_label(ll)
]
# Validate all labels
all_labels = set(instance.labels) | set(instance.effective_labels)
can_set_label = getattr(sender, "can_set_label", lambda x: True)
for label in Label.objects.filter(name__in=list(all_labels)):
if not can_set_label(label):
# Check can_set_label method
raise ValueError(f"Invalid label: {label.name}")
all_labels.discard(label.name)
if all_labels:
raise ValueError(f"Invalid labels: {', '.join(all_labels)}")
# Install handlers
if is_document(m_cls):
from mongoengine import signals as mongo_signals
mongo_signals.pre_save.connect(on_pre_save,
sender=m_cls,
weak=False)
else:
from django.db.models import signals as django_signals
django_signals.pre_save.connect(on_pre_save,
sender=m_cls,
weak=False)
return m_cls