136 lines
3.8 KiB
Python
136 lines
3.8 KiB
Python
from collections import defaultdict
|
|
import itertools
|
|
import sqlalchemy as sa
|
|
import six
|
|
|
|
|
|
class AttributeValueGenerator(object):
|
|
def __init__(self):
|
|
self.reset()
|
|
|
|
def reset(self):
|
|
self.generator_registry = defaultdict(list)
|
|
self.listeners_registered = False
|
|
|
|
def generator_wrapper(self, func, attr):
|
|
def wrapper(self, *args, **kwargs):
|
|
return func(self, *args, **kwargs)
|
|
|
|
if isinstance(attr, six.string_types) and '.' in attr:
|
|
parts = attr.split('.')
|
|
self.generator_registry[parts[0]].append(wrapper)
|
|
wrapper.__generates__ = parts[1]
|
|
elif isinstance(attr, sa.orm.attributes.InstrumentedAttribute):
|
|
self.generator_registry[attr.class_.__name__].append(wrapper)
|
|
wrapper.__generates__ = attr
|
|
else:
|
|
wrapper.__generates__ = attr
|
|
return wrapper
|
|
|
|
def register_listeners(self):
|
|
if not self.listeners_registered:
|
|
sa.event.listen(
|
|
sa.orm.mapper,
|
|
'mapper_configured',
|
|
self.update_generator_registry
|
|
)
|
|
sa.event.listen(
|
|
sa.orm.session.Session,
|
|
'before_flush',
|
|
self.update_generated_properties
|
|
)
|
|
self.listeners_registered = True
|
|
|
|
def update_generator_registry(self, mapper, class_):
|
|
for value in class_.__dict__.values():
|
|
if hasattr(value, '__generates__'):
|
|
self.generator_registry[class_.__name__].append(value)
|
|
|
|
def update_generated_properties(self, session, ctx, instances):
|
|
for obj in itertools.chain(session.new, session.dirty):
|
|
class_ = obj.__class__.__name__
|
|
if class_ in self.generator_registry:
|
|
for func in self.generator_registry[class_]:
|
|
attr = func.__generates__
|
|
if not isinstance(attr, six.string_types):
|
|
attr = attr.name
|
|
setattr(obj, attr, func(obj))
|
|
|
|
|
|
generator = AttributeValueGenerator()
|
|
|
|
|
|
def generates(attr, generator=generator):
|
|
"""
|
|
Many times you may have generated property values. Usual cases include
|
|
slugs from names or resized thumbnails from images.
|
|
|
|
SQLAlchemy-Utils provides a way to do this easily with `generates`
|
|
decorator:
|
|
|
|
::
|
|
|
|
|
|
class Article(Base):
|
|
__tablename__ = 'article'
|
|
id = sa.Column(sa.Integer, primary_key=True)
|
|
name = sa.Column(sa.Unicode(255))
|
|
slug = sa.Column(sa.Unicode(255))
|
|
|
|
@generates(slug)
|
|
def _create_slug(self):
|
|
return self.name.lower().replace(' ', '-')
|
|
|
|
|
|
article = self.Article()
|
|
article.name = u'some article name'
|
|
self.session.add(article)
|
|
self.session.flush()
|
|
assert article.slug == u'some-article-name'
|
|
|
|
|
|
You can also pass the attribute name as a string argument for `generates`:
|
|
|
|
::
|
|
|
|
class Article(Base):
|
|
...
|
|
|
|
@generates('slug')
|
|
def _create_slug(self):
|
|
return self.name.lower().replace(' ', '-')
|
|
|
|
|
|
These property generators can even be defined outside classes:
|
|
|
|
::
|
|
|
|
|
|
class Article(Base):
|
|
__tablename__ = 'article'
|
|
id = sa.Column(sa.Integer, primary_key=True)
|
|
name = sa.Column(sa.Unicode(255))
|
|
slug = sa.Column(sa.Unicode(255))
|
|
|
|
|
|
@generates(Article.slug)
|
|
def _create_article_slug(article):
|
|
return article.name.lower().replace(' ', '-')
|
|
|
|
|
|
Or with lazy evaluated string argument:
|
|
|
|
::
|
|
|
|
|
|
@generates('Article.slug')
|
|
def _create_article_slug(article):
|
|
return article.name.lower().replace(' ', '-')
|
|
"""
|
|
|
|
generator.register_listeners()
|
|
|
|
def wraps(func):
|
|
return generator.generator_wrapper(func, attr)
|
|
return wraps
|