Django模型定义种族 [英] Django Model Definition Race

问题描述

如何处理您有一个依赖于模型（B）被定义的模型（A）的情况，但是模型（B）也依赖于定义的模型（A）。

例如，我有

 类事件（models.Model）：
 competition_start = models.DateField（）
 competitors = models.ManyToManyField（picture）
 results = models.CommaSeparatedIntegerField（max_length = 20）
 
类图片（models.Model）：
 uploader = models.OneToOneField（UserProfile）
 upload_date = models.DateField（）
 image = models.ImageField（upload_to =media）
 score = models.DecimalField（max_digits = 10 ，decimal_places = 10）
 score_RD = models.DecimalField（max_digits = 10，decimal_places = 10）
 rated = models.BooleanField（）
 last_competed = models.DateField（）
竞争= models.OneToOneField（event）
  

竞争对手领域依赖于定义的图片，但图片依赖于ev被定义。请注意，每张图片（A）与事件共享一对一关系，但事件可能涉及多个其他图片（set（S）-A）。

我尝试交换到

  competitors = models.ManyToManyField （图）
 user_pic = models.OneToOneField（图片）
  

内部的事件和摆脱的领域'竞争'，但我相信SQL不允许这个。有人可以解释为什么吗？

如果我需要一个字段的OneToOne关系和
与另一个字段的ManyToMany关系，我应该执行什么修复？ （在两个相同的类之间）

谢谢：）

解决方案

您可以将类名的字符串传递给 OneToOne 和 ForeignKey 的定义，并将其评估为懒惰

  competitors = models.ManyToManyField（'picture'）
  

此外，模型类名称的惯例是camel-case（例如'picture'=>'Picture'，'event'=>'Event'）。 p>

How do you deal with the case where you have a model (A) that relies on model (B) being defined, but model (B) also relies on model(A) being defined.

For instance, I have

class event(models.Model):
    competition_start = models.DateField() 
    competitors = models.ManyToManyField(picture)
    results = models.CommaSeparatedIntegerField(max_length=20)

class picture(models.Model):
    uploader = models.OneToOneField(UserProfile)
    upload_date = models.DateField()
    image = models.ImageField(upload_to="media")
    score = models.DecimalField(max_digits=10,decimal_places=10)
    score_RD = models.DecimalField(max_digits=10,decimal_places=10)
    rated = models.BooleanField()
    last_competed = models.DateField() 
    competition = models.OneToOneField(event) 

The competitors field relies on picture being defined but picture relies on event being defined.

Note that each picture (A) shares a one to one relationship with an event, but the event can involve multiple other pictures (set(S)-A).

I tried swapping over to putting

competitors = models.ManyToManyField(picture) 
user_pic = models.OneToOneField(picture)

inside of event and getting rid of the field 'competition', but I believe SQL does not allow this. Can someone explain why?

What fix should I perform if I need a OneToOne relationship for one field and a ManyToMany relationship with another? (between the two same classes)

Thank you :)

解决方案

You can pass in the string of the class name to the definition of OneToOne and ForeignKey and have it evaluated "lazily".

competitors = models.ManyToManyField('picture')

Also, the convention for model class names is camel-case (e.g. 'picture' => 'Picture', 'event' => 'Event').

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