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
|
"""
41. Tests for select_related()
``select_related()`` follows all relationships and pre-caches any foreign key
values so that complex trees can be fetched in a single query. However, this
isn't always a good idea, so the ``depth`` argument control how many "levels"
the select-related behavior will traverse.
"""
from django.db import models
from django.utils.encoding import python_2_unicode_compatible
# Who remembers high school biology?
@python_2_unicode_compatible
class Domain(models.Model):
name = models.CharField(max_length=50)
def __str__(self):
return self.name
@python_2_unicode_compatible
class Kingdom(models.Model):
name = models.CharField(max_length=50)
domain = models.ForeignKey(Domain)
def __str__(self):
return self.name
@python_2_unicode_compatible
class Phylum(models.Model):
name = models.CharField(max_length=50)
kingdom = models.ForeignKey(Kingdom)
def __str__(self):
return self.name
@python_2_unicode_compatible
class Klass(models.Model):
name = models.CharField(max_length=50)
phylum = models.ForeignKey(Phylum)
def __str__(self):
return self.name
@python_2_unicode_compatible
class Order(models.Model):
name = models.CharField(max_length=50)
klass = models.ForeignKey(Klass)
def __str__(self):
return self.name
@python_2_unicode_compatible
class Family(models.Model):
name = models.CharField(max_length=50)
order = models.ForeignKey(Order)
def __str__(self):
return self.name
@python_2_unicode_compatible
class Genus(models.Model):
name = models.CharField(max_length=50)
family = models.ForeignKey(Family)
def __str__(self):
return self.name
@python_2_unicode_compatible
class Species(models.Model):
name = models.CharField(max_length=50)
genus = models.ForeignKey(Genus)
def __str__(self):
return self.name
# and we'll invent a new thing so we have a model with two foreign keys
@python_2_unicode_compatible
class HybridSpecies(models.Model):
name = models.CharField(max_length=50)
parent_1 = models.ForeignKey(Species, related_name='child_1')
parent_2 = models.ForeignKey(Species, related_name='child_2')
def __str__(self):
return self.name
|
