如何与 "through" 模型的父模型建立 "related_name" 关系（关于 related_name 继承）

Question

我有 4 个模型，包括一个 M2M“直通”模型，可以有一个索引：

class TargetShape(models.Model):
    pass
    
class Page(models.Model):
    target_shapes = models.ManyToManyField(TargetShape, through='PageElement', related_name='pages')
    
class PageElement(models.Model):
    target_shape = models.ForeignKey(TargetShape, related_name='page_elements')
    page = models.ForeignKey(Page, related_name='page_elements')
    index = models.PositiveIntegerField(verbose_name='Order')
    

class WorkingSession(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='working_sessions')

我定义了另一个模型 Resolution，它使我能够 link 所有这些，以便创建以下 related_name 关系：

working_session.resolutions
user.resolutions
target_shape.resolutions
page.resolutions
page_element.resolutions

要让它正常工作，我必须声明：

class Resolution(models.Model):
    # relations that would be needed from a DRY perspective:
    page_element = models.ForeignKey(PageElement, related_name='resolutions')
    working_session = models.ForeignKey(WorkingSession, related_name='resolutions')
    
    # relations I want to exist to use user.resolutions, target_shape.resolutions, page.resolutions: 
    user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='resolutions')
    target_shape = models.ForeignKey(TargetShape, related_name='resolutions')
    page = models.ForeignKey(Page, related_name='resolutions')

但是，这不是很干。从 DRY 的角度来看，我应该能够将 Resolution 声明为 linking 到 PageElement 和 WorkingSession，并推断/继承与父模型的关系：

class Resolution(models.Model):
    page_element = models.ForeignKey(PageElement, related_name='resolutions')
    working_session = models.ForeignKey(WorkingSession, related_name='resolutions')

但在那种情况下，我如何创建以下关系：

user.resolutions
target_shape.resolutions
page.resolutions

不经过：

user.working_sessions.resolutions
target_shape.page_elements.resolutions
page.page_elements.resolutions

Answer 1

我能想到的就是：

要么像我已经做的那样声明所有字段
或在 User、TargetShape 和 Page 模型中声明一个属性分别 returns:

Resolution.objects.filter(working_session__user=自己) Resolution.objects.filter(page_element__target_shape=自己) Resolution.objects.filter(page_element__page=自己)

那肯定行得通，但这不是很优雅......而且不是很像 Django

有人知道定义这种关系的更像 Django 的方法吗？

Answer 2

我发现了另一种方法：在 User、TargetShape 和 Page 模型中声明一个属性 returns 一个查询集：

class Resolution(models.Model):
    page_element = models.ForeignKey(PageElement, related_name='resolutions')
    working_session = models.ForeignKey(WorkingSession, related_name='resolutions')

class PageElement(models.Model):
    target_shape = models.ForeignKey(TargetShape, related_name='page_elements')
    page = models.ForeignKey(Page, related_name='page_elements')
    index = models.PositiveIntegerField(verbose_name='Order')
    

class WorkingSession(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='working_sessions')



class TargetShape(models.Model):
    @property
    def resolutions(self):
        return Resolution.objects.filter(page_element__target_shape=self) 

    
class Page(models.Model):
    @property
    def resolutions(self):
        return Resolution.objects.filter(page_element__page=self)

    target_shapes = models.ManyToManyField(TargetShape, through='PageElement', related_name='pages')

如何与 "through" 模型的父模型建立 "related_name" 关系（关于 related_name 继承）

How to create "related_name" relation with parent models of "through" model (about related_name inheritance)

django

django-models

django-orm