Django:一个模型中有多个泛型关系，设计不好

Question

我有一个具有多个泛型关系的模型，在我的模板中使用它变得非常复杂。该模型是在"场地"和/或"音乐节"举行的"Gig"或音乐活动，并有一个"音乐家"和/或者"合奏团"。

更复杂的是，每个"Gig"都有一个主持人、推广人和经纪人。这些设置为与其他模型（如"PresenterCompany"）的通用关系。Presenter公司可以是一个推广人、演示者或代理人，也可以是同一场演出的所有人。以下是模型（简化以供参考）：

class Gig(models.Model):
    description = models.CharField(max_length=100, blank=True)
    date = models.DateTimeField()
    venue = models.ForeignKey(Venue)
    festival = models.ForeignKey(Festival, blank = True, null=True)
    musician = models.ManyToManyField(Musician, blank=True)
    ensembles = models.ManyToManyField(Ensemble, blank = True)
    presenter_content_type = models.ForeignKey(ContentType,
        limit_choices_to={"model__in": ("Individual", "ArtsOrganization",'Presenter', "BookingAgent","Festival", "OtherOrganization","PresenterCompany", "Venue")}, related_name = "Presenter Type", verbose_name = "Presenter",blank=True, null=True)
    presenter_id = models.IntegerField(db_index=True, blank=True, null=True, verbose_name='Presenter ID')
    presenter = generic.GenericForeignKey('presenter_content_type','presenter_id')
    promoter_content_type = models.ForeignKey(ContentType,
        limit_choices_to={"model__in": ("Individual", "ArtsOrganization","BookingAgent","Presenter", "Festival", "OtherOrganization","PresenterCompany", "Venue")}, related_name = "promotor", verbose_name='Promoter Type', blank=True, null=True)
    promoter_id = models.IntegerField(db_index=True, blank=True, null=True, verbose_name='Promoter ID')
    promoter = generic.GenericForeignKey('promoter_content_type','promoter_id')
    agent_content_type = models.ForeignKey(ContentType,
        limit_choices_to={"model__in": ("Individual", "BookingAgent")}, related_name="agent", verbose_name='Agent Type', blank=True, null=True)
    agent_id = models.IntegerField(db_index=True, blank=True, null=True, verbose_name='Agent ID')
    agent = generic.GenericForeignKey('agent_content_type','agent_id')

class PresenterCompany(models.Model):
    name = models.CharField(max_length=70)
    address =GenericRelation(Address)
    presented_gig = GenericRelation('Gig',
        content_type_field='presenter_content_type',
        object_id_field='presenter_id',
        related_name='presenter_presented_gig'
    )
    promoted_gig = GenericRelation('Gig',
        content_type_field='promoter_content_type',
        object_id_field='promoter_id',
        related_name='presenter_promoted_gig'
    )
    booked_gig = GenericRelation('Gig',
        content_type_field='promoter_content_type',
        object_id_field='promoter_id',
        related_name='presenter_booked_gig'
    )

主要的问题是，当我试图获得一家演讲者公司的所有演出时，我必须为每个角色写三个不同的for循环，即{%for gig in presentcorporaty.presentd_gig.all%}，依此类推……这似乎是多余的代码。

有没有更好的方法来构建它，比如使用演示者、发起人和代理的中介模型？谢谢你的建议！

Answer 1

泛型关系肯定很难处理。只有在没有其他选择的情况下，我才会使用它们。

在你的情况下，我看到了其他几种选择。PresenterCompany和Gig之间可以有一个ManyToMany关系，使用直通表指定关系类型(https://docs.djangoproject.com/en/2.0/topics/db/models/#extra-多对多关系上的字段）：

class Gig(models.Model):
    description = models.CharField(max_length=100, blank=True)
    date = models.DateTimeField()
    venue = models.ForeignKey(Venue)
    festival = models.ForeignKey(Festival, blank=True, null=True)
    musician = models.ManyToManyField(Musician, blank=True)
    ensembles = models.ManyToManyField(Ensemble, blank=True)

class PresenterCompanyGigRelationship(models.Model):
    gig = models.ForeignKey(Gig, on_delete=models.CASCADE)
    presenter_company = models.ForeignKey(
        'PresenterCompany', on_delete=models.CASCADE)
    relationship = models.CharField(
        max_length=10,
        choices=(
            ('presenter', 'Presenter'),
            ('promoter', 'Promoter'),
            ('agent', 'Agent'),
            ))

class PresenterCompany(models.Model):
    name = models.CharField(max_length=70)
    git = models.ManyToManyField(Gig, through=PresenterCompanyGigRelationship)