mirror of
https://github.com/Hopiu/django-model-utils.git
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74 lines
2.8 KiB
Python
74 lines
2.8 KiB
Python
from types import ClassType
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from django.db import models
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from django.db.models.manager import Manager
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from django.db.models.query import QuerySet
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class QueryManager(models.Manager):
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def __init__(self, *args, **kwargs):
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if args:
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self._q = args[0]
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else:
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self._q = models.Q(**kwargs)
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super(QueryManager, self).__init__()
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def order_by(self, *args):
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self._order_by = args
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return self
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def get_query_set(self):
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qs = super(QueryManager, self).get_query_set().filter(self._q)
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if hasattr(self, '_order_by'):
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return qs.order_by(*self._order_by)
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return qs
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def manager_from(*mixins, **kwds):
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'''
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Returns a Manager instance with extra methods, also available and
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chainable on generated querysets.
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(By George Sakkis, originally posted at
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http://djangosnippets.org/snippets/2117/)
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:param mixins: Each ``mixin`` can be either a class or a function. The
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generated manager and associated queryset subclasses extend the mixin
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classes and include the mixin functions (as methods).
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:keyword queryset_cls: The base queryset class to extend from
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(``django.db.models.query.QuerySet`` by default).
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:keyword manager_cls: The base manager class to extend from
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(``django.db.models.manager.Manager`` by default).
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'''
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# collect separately the mixin classes and methods
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bases = [kwds.get('queryset_cls', QuerySet)]
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methods = {}
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for mixin in mixins:
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if isinstance(mixin, (ClassType, type)):
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bases.append(mixin)
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else:
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try: methods[mixin.__name__] = mixin
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except AttributeError:
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raise TypeError('Mixin must be class or function, not %s' %
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mixin.__class__)
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# create the QuerySet subclass
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id = hash(mixins + tuple(kwds.iteritems()))
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new_queryset_cls = type('Queryset_%d' % id, tuple(bases), methods)
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# create the Manager subclass
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bases[0] = manager_cls = kwds.get('manager_cls', Manager)
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new_manager_cls = type('Manager_%d' % id, tuple(bases), methods)
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# and finally override new manager's get_query_set
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super_get_query_set = manager_cls.get_query_set
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def get_query_set(self):
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# first honor the super manager's get_query_set
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qs = super_get_query_set(self)
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# and then try to bless the returned queryset by reassigning it to the
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# newly created Queryset class, though this may not be feasible
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if not issubclass(new_queryset_cls, qs.__class__):
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raise TypeError('QuerySet subclass conflict: cannot determine a '
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'unique class for queryset instance')
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qs.__class__ = new_queryset_cls
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return qs
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new_manager_cls.get_query_set = get_query_set
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return new_manager_cls()
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