在此提出了两个关键问题。 <>First: How is choice_set calls into existence. <>秒钟>: 是什么?
对于像我这样的所有新发展者,让我描述我如何使我容易。 让我首先回答第二个问题。 通过这三字“是什么?” Modelase, Object-set related to that instance, Related_manager。
Django 辅导模型:
from django.db import models
class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField( date published )
class Choice(models.Model):
question = models.ForeignKey(Question, on_delete=models.CASCADE)
choice_text = models.CharField(max_length=200)
votes = models.IntegerField(default=0)
<>Instance:
q = Question.objects.get(pk=3)
# Here q is an instance of model class Question .
c = Choice.objects.get(pk=32)
# Here c is an instance of model class Choice .
Model Instance is a single ROW of an entire TABLE of your database
此处的<编码> 问题示范作为<代码>foreign key至 选择模型。 因此,所有objects-set与e.q有关 可以通过使用:
q.choice_set.all()
因此,choice_set,此处指与问题有关的所有选择,即:pk=3。
现在,第一个问题的答复需要第三字 Relatd Manager。 Django 文件here:-
If a model has a ForeignKey, instances of the foreign-key model will
have access to a Manager that returns all instances of the first
model. By default, this Manager is named FOO_set, where FOO is the
source model name, lowercased. This Manager returns QuerySets, which
can be filtered and manipulated as described in the “Retrieving
objects” section above.
可以用外在钥匙中的相关“姓名参数”来改变这个词(组)。
question = models.ForeignKey(Question, on_delete=models.CASCADE, related_name="choices")
外国钥匙的后向关系:
q.choice_set.all()
# If using related_name, then it is same as
q.choices.all()
# All the choices related to the instance q.
前瞻性关系:
choice_qs = Choice.objects.all()
choice_qs.filter(question=q)
# Same result as above. All the choices related to instance q.
