来自同一 object 的 2 个不同引用到来自同一 class - DJANGO 数据库的两个不同对象

Question

I want to have a match object with two team references. IE(old json database example):
I would like to easeliy be able to access each team and possibly swap side. That's why I want to use Django example 2, as then I can reference each team from the Match Object. But example gives an error about each reference duplicating each other...

{
  "dateTime": "",
  "matchID":"0fb86bcf-c700-4429-b5a9-558ca9b95a03",
  "team1ID":"e372b7f4-008f-4503-beee-1d6756361fea",
  "team2ID":"802b4705-d812-4a88-9246-b14bd18938d8",
  "format":3,
  "division":"Relegation",
  "league":leagueRef,
  "game":leagueRef,
}

Django example 1:

class Match(models.Model):
    ...
    team = models.ManyToManyField(
        Team,
        on_delete=models.CASCADE,
        )

Django example 2:

class Match(models.Model):
    ...
    team1 = models.OneToOneField(
         Team,
         on_delete=models.CASCADE,
         )
    team2 = models.OneToOneField(
         Team,
         on_delete=models.CASCADE,
         )

Answer 1

When one uses a OneToOneField (or any other related field) Django automatically makes a reverse accessor on the other side of the relation. So in the model team Django will automatically make an attribute with the name match to access this related object. The problem is you have two of these fields making Django not know what name to use for them.

You can solve this by specifying a related_name [Django docs] :

class Match(models.Model):
    ...
    team1 = models.OneToOneField(
        Team,
        on_delete=models.CASCADE,
        related_name='match_1'
    )
    team2 = models.OneToOneField(
        Team,
        on_delete=models.CASCADE,
        related_name='match_2'
    )

Note : By using a OneToOneField it means that one team can only have one entry in the Match table (once from both sides). So in essence with this a team can only be in 2 matches. Perhaps you want to use a ForeignKey [Django docs] instead.