Ticket #17270: manager.py

File manager.py, 4.3 KB (added by Wojciech Banaś <fizista@…>, 13 years ago)

New manager class

Line 
1from types import MethodType
2from django.db import models
3from django.db.models.query import QuerySet
4
5def applicate_method_list(queryset_object):
6 """
7 Convert method list to object attribute.
8 """
9 manager_method_list = getattr(queryset_object, '_manager_method_list')
10 for query_method in manager_method_list:
11 try:
12 getattr(queryset_object, query_method.__name__)
13 break
14 except AttributeError:
15 setattr(queryset_object, query_method.__name__, query_method)
16 return queryset_object
17
18def manager_methods_in_queryset(_clone_method):
19 """
20 Decorator for method '_clone' in object QuerySet
21 """
22 def _clone_decorator(*args, **kwargs):
23 c = _clone_method(*args, **kwargs)
24 if not hasattr(c, '_manager_method_list') and hasattr(args[0], '_manager_method_list'):
25 c._manager_method_list = getattr(args[0], '_manager_method_list')
26 applicate_method_list(c)
27 return c
28 return _clone_decorator
29
30class ManagerQuerySetDecorator(models.Manager):
31 """
32 Extends the operation methods of the manager on subqueries QuerySet objects.
33
34 The "standard manager" you can only like this:
35 SomeModel.object.some_method_manager().all().filter(...). ...
36
37 But this does not work:
38 SomeModel.object.all().some_method_manager()
39
40 And this it works with the use of this class / patches:
41 SomeModel.object.all().some_method_manager().filter(...).some_method_manager2(). ...
42 SomeModel.object.some_method_manager().some_method_manager2().some_method_manager3(). ...
43
44 Extension of the methods manager on all child objects "QuerySeth".
45
46 Example:
47
48 class Animals(models.Model):
49 type = models.CharField('Type of animal') # dog, cat, elephant
50 color = models.CharField('Colour Name')
51
52 objects = AnimalsManager()
53
54 class AnimalsManager(ManagerQuerySetDecorator):
55
56 def get_dogs(self):
57 return self.get_query_set().filter(type='dog')
58 get_dogs.queryset_method = True
59
60 def get_cats(self):
61 return self.get_query_set().filter(type='cat')
62 get_cats.queryset_method = True
63
64 def get_white_animals(self):
65 return self.get_query_set().filter(color='white')
66 get_white_animals.queryset_method = True
67
68 def get_black_animals(self):
69 return self.get_query_set().filter(color='black')
70 get_black_animals.queryset_method = True
71
72 def get_brown_animals(self):
73 return self.get_query_set().filter(color='black')
74
75
76 Animals(type='dog', color='black').save()
77 Animals(type='dog', color='bown').save()
78 Animals(type='dog', color='white').save()
79 Animals(type='cat', color='black').save()
80 Animals(type='cat', color='bown').save()
81 Animals(type='cat', color='white').save()
82
83 animals = Animals.objects.get_black_animals().get_dogs()
84 # return list black dogs
85
86 animals = Animals.objects.get_white_animals().get_cats()
87 # return list white cats
88
89 # When ffff equals False, or not defined (as it is in
90 # the original model manager), we can not perform such an operation:
91 animals = Animals.objects.get_cats().get_brown_animals()
92 # return:
93 # AttributeError: 'QuerySet' object has no attribute 'get_brown_animals'
94
95 # but:
96 animals = Animals.objects.get_brown_animals().get_cats()
97 # return brown cats, because get_cat() present in all parent object instances.
98 """
99 def __init__(self):
100 super(ManagerQuerySetDecorator, self).__init__()
101 # Method _clone decoration if it was not previously decorated
102 if not getattr(QuerySet._clone, '__name__') == '_clone_decorator':
103 QuerySet._clone = manager_methods_in_queryset(QuerySet._clone)
104
105 def get_query_set(self):
106 qs = super(ManagerQuerySetDecorator, self).get_query_set()
107 list_arrtibutes = [getattr(self,attrib_name) for attrib_name in dir(self)]
108 for attr in list_arrtibutes:
109 if isinstance(attr, MethodType) and hasattr(attr, 'queryset_method') and attr.queryset_method:
110 try:
111 qs._manager_method_list += [attr]
112 except AttributeError:
113 qs._manager_method_list = [attr]
114 applicate_method_list(qs)
115 return qs
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