Django在保存时更新m2m对象

我有m-2-m相对值和i want to update the rel B after any rel A is added via the admin page.

Here the details:

我有2个型号，Match(rel A)和Player(rel B).我想更新Player.matches_played，每次在Match.team1或Match.team2中添加与该球员的新比赛.

How can i achieve this???

模型

class Match(models.Model):
    data=models.DateField(auto_now_add=False,auto_now=False)
    team1=models.ManyToManyField('players.Player',related_name='team_1')
    team2=models.ManyToManyField('players.Player',related_name='team_2')
    score_team1=models.IntegerField(validators=[MinValueValidator(0)])
    score_team2=models.IntegerField(validators=[MinValueValidator(0)])

class Player(models.Model):
    matches_played= models.IntegerField(validators=[MinValueValidator(0)], default=0)

I tried signals，但在post_save signal {instance.team1}或instance.team1.all()中返回an empty QuerySet，我认为这是正确的，因为M2M rel稍后会保存. 然后我try 了m2m_changed，但信号为is not fired，并通过管理页面保存.我错过了什么？

@receiver(post_save, sender=Match, dispatch_uid="update_player_game_count")
def update_player_games(sender, instance, created, **kwargs):
    print(f'created {instance.pk}')
    print(f'created {instance.team1}')
    print(f'created {instance.team2}')
    print(f'created {instance.score_team1}')
    print(instance.team1.all())

@receiver(m2m_changed, sender=Match, dispatch_uid="update_player_game_count")
def update_player_game(sender, instance, created, action, **kwargs):
    print(action)
    if action == 'post_add':
        print(action)

非常感谢您的帮助

我想到的是an alternative是通过Player中的属性检索数据，例如这样，but我认为，from a performance point of view，最好在每次添加匹配时更新行，然后在每次请求玩家时计算匹配数

例如

@property
def matches_played(self):
    return Match.objects.filter(team1__nome=self.nome).count()+Match.objects.filter(team2__nome=self.nome).count()