我有一个带有多个Question对象的django应用。问题和测验通过ManyToManyField相关联。我想创建测验对象,以便每个测验被随机分配3个问题。
我已经尝试在模型中创建一个保存方法,在该模型中,我:使用查询集获取3个问题,保存测验实例(以保存ID),将查询集设置为测验,然后再次保存。我在该主题上进行的大多数搜索都显示出人们在哪里使用表单保存m2m对象。
甚至更好,是否可以使用视图向一个测验对象设置3个问题?最终,这是我想要去的地方。用户将在视图中使用request.GET选择LearnGoal,并且此LearnGoal将限制将添加到测验中的问题。
到目前为止,我的models.py:
class LearnGoal(models.Model):
goal_name = models.CharField(max_length=12)
goal_description = models.TextField()
class Question(models.Model):
name = models.CharField(max_length=12)
learngoal = models.ForeignKey(LearnGoal, on_delete=models.CASCADE)
q_text = models.TextField()
answer = models.CharField(max_length=12)
class Quiz(models.Model):
"""quiz which will have three questions."""
name = models.CharField(max_length=12)
questions = models.ManyToManyField(Question)
completed = models.DateTimeField(auto_now_add=True)
my_answer = models.CharField(max_length=12)
def save(self, *args, **kwargs):
"""need to create an instance first, for the m2m"""
super(Quiz, self).save(*args, **kwargs)
"""get 3 random questions"""
three_questions = Quiz.objects.all().order_by('?')[0:3]
self.questions.set(three_questions)
super(Quiz, self).save(*args, **kwargs)
我已经尝试了上述代码的一些变体。当前,此代码给出错误:'Question' instance expected, got <Quiz: Quiz object (4)>
行中的self.questions.set(five_questions)
如何将多个问题保存到一个测验实例中?
在Quiz.save
方法中,您可以执行以下操作:
class Quiz(models.Model):
...
...
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.add_questions = False
def save(self, *args, **kwargs):
# We need this to prevent updating questions
# on updating the Quiz instance
if self.pk is None:
self.add_questions = True
super().save(*args, **kwargs)
if self.add_questions:
# No need to run save again; M2M relationships are set
# through an intermediate model
self.questions.set(Question.objects.order_by('?')[:3])
请注意,随机排序(order_by('?')
)速度很慢,但这是否会完全影响您取决于使用情况。