1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
|
"""
By specifying the 'proxy' Meta attribute, model subclasses can specify that
they will take data directly from the table of their base class table rather
than using a new table of their own. This allows them to act as simple proxies,
providing a modified interface to the data from the base class.
"""
from django.db import models
# A couple of managers for testing managing overriding in proxy model cases.
class PersonManager(models.Manager):
def get_queryset(self):
return super().get_queryset().exclude(name="fred")
class SubManager(models.Manager):
def get_queryset(self):
return super().get_queryset().exclude(name="wilma")
class Person(models.Model):
"""
A simple concrete base class.
"""
name = models.CharField(max_length=50)
objects = PersonManager()
def __str__(self):
return self.name
class Abstract(models.Model):
"""
A simple abstract base class, to be used for error checking.
"""
data = models.CharField(max_length=10)
class Meta:
abstract = True
class MyPerson(Person):
"""
A proxy subclass, this should not get a new table. Overrides the default
manager.
"""
class Meta:
proxy = True
ordering = ["name"]
permissions = (("display_users", "May display users information"),)
objects = SubManager()
other = PersonManager()
def has_special_name(self):
return self.name.lower() == "special"
class ManagerMixin(models.Model):
excluder = SubManager()
class Meta:
abstract = True
class OtherPerson(Person, ManagerMixin):
"""
A class with the default manager from Person, plus a secondary manager.
"""
class Meta:
proxy = True
ordering = ["name"]
class StatusPerson(MyPerson):
"""
A non-proxy subclass of a proxy, it should get a new table.
"""
status = models.CharField(max_length=80)
objects = models.Manager()
# We can even have proxies of proxies (and subclass of those).
class MyPersonProxy(MyPerson):
class Meta:
proxy = True
class LowerStatusPerson(MyPersonProxy):
status = models.CharField(max_length=80)
objects = models.Manager()
class User(models.Model):
name = models.CharField(max_length=100)
def __str__(self):
return self.name
class UserProxy(User):
class Meta:
proxy = True
class AnotherUserProxy(User):
class Meta:
proxy = True
class UserProxyProxy(UserProxy):
class Meta:
proxy = True
class MultiUserProxy(UserProxy, AnotherUserProxy):
class Meta:
proxy = True
# We can still use `select_related()` to include related models in our querysets.
class Country(models.Model):
name = models.CharField(max_length=50)
class State(models.Model):
name = models.CharField(max_length=50)
country = models.ForeignKey(Country, models.CASCADE)
def __str__(self):
return self.name
class StateProxy(State):
class Meta:
proxy = True
# Proxy models still works with filters (on related fields)
# and select_related, even when mixed with model inheritance
class BaseUser(models.Model):
name = models.CharField(max_length=255)
def __str__(self):
return ":".join(
(
self.__class__.__name__,
self.name,
)
)
class TrackerUser(BaseUser):
status = models.CharField(max_length=50)
class ProxyTrackerUser(TrackerUser):
class Meta:
proxy = True
class Issue(models.Model):
summary = models.CharField(max_length=255)
assignee = models.ForeignKey(
ProxyTrackerUser, models.CASCADE, related_name="issues"
)
def __str__(self):
return ":".join(
(
self.__class__.__name__,
self.summary,
)
)
class Bug(Issue):
version = models.CharField(max_length=50)
reporter = models.ForeignKey(BaseUser, models.CASCADE)
class ProxyBug(Bug):
"""
Proxy of an inherited class
"""
class Meta:
proxy = True
class ProxyProxyBug(ProxyBug):
"""
A proxy of proxy model with related field
"""
class Meta:
proxy = True
class Improvement(Issue):
"""
A model that has relation to a proxy model
or to a proxy of proxy model
"""
version = models.CharField(max_length=50)
reporter = models.ForeignKey(ProxyTrackerUser, models.CASCADE)
associated_bug = models.ForeignKey(ProxyProxyBug, models.CASCADE)
class ProxyImprovement(Improvement):
class Meta:
proxy = True
|
