Django相关字段的正确使用

Question

Django 模型的一个方面是我根本不了解的相关字段，以及如何正确使用它们。我认为这反映出对 SQL 和一般数据库的理解不足 - 所以我怀疑这对许多 django 用户来说是个问题。

在我当前的代码中，我正在构建一个旅游应用程序，因此我将 Accommodation 作为模型。然后我有路线。这一天的路线最终变成了一堆关系领域，但让我感到困惑的是我需要一个开始住宿和一个结束住宿 - 两个独立的关系。

对我来说，按理来说，我应该可以有一个OneToOneField——start_accom来住宿，然后end_accom来住宿。但是这样做会引发错误。

代码：

class Route(models.Model):                                                                                                  
    start_accom = models.OneToOneField(                                                                                     
        Accommodation,                                                                                                      
        on_delete=models.CASCADE,                                                                                           
        primary_key=True,                                                                                                   
    )                                                                                                                       
    end_accom = models.OneToOneField(                                                                                                                                                                             
        Accommodation,                                                                                                      
        on_delete=models.CASCADE,                                                                                           
    )                                                                                                                       
    mode_of_travel = models.CharField(max_length=50)                                                                        
    description = models.TextField()

以及当我运行 django 运行server 时的错误信息：

Performing system checks...

Unhandled exception in thread started by <function check_errors.<locals>.wrapper at 0x103ecdd90>
Traceback (most recent call last):
  File "/Users/vernonswanepoel/.virtualenvs/tour/lib/python3.6/site-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)
  File "/Users/vernonswanepoel/.virtualenvs/tour/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 121, in inner_run
    self.check(display_num_errors=True)
  File "/Users/vernonswanepoel/.virtualenvs/tour/lib/python3.6/site-packages/django/core/management/base.py", line 431, in check
    raise SystemCheckError(msg)
django.core.management.base.SystemCheckError: SystemCheckError: System check identified some issues:

ERRORS:
company.Route.end_accom: (fields.E304) Reverse accessor for 'Route.end_accom' clashes with reverse accessor for 'Route.start_accom'.
        HINT: Add or change a related_name argument to the definition for 'Route.end_accom' or 'Route.start_accom'.
company.Route.end_accom: (fields.E305) Reverse query name for 'Route.end_accom' clashes with reverse query name for 'Route.start_accom'.
        HINT: Add or change a related_name argument to the definition for 'Route.end_accom' or 'Route.start_accom'.
company.Route.start_accom: (fields.E304) Reverse accessor for 'Route.start_accom' clashes with reverse accessor for 'Route.end_accom'.
        HINT: Add or change a related_name argument to the definition for 'Route.start_accom' or 'Route.end_accom'.
company.Route.start_accom: (fields.E305) Reverse query name for 'Route.start_accom' clashes with reverse query name for 'Route.end_accom'.
        HINT: Add or change a related_name argument to the definition for 'Route.start_accom' or 'Route.end_accom'.

System check identified 4 issues (0 silenced).

Answer 1

这个问题，正如它提到的那样，是因为反向关系。你需要 add the related_name attribute

class Route(models.Model):                                                                                                  
    start_accom = models.OneToOneField(                                                                                     
        Accommodation,                                                                                                      
        on_delete=models.CASCADE,                                                                                           
        primary_key=True, 
        related_name="accommodation_start"                                                                                                  
    )                                                                                                                       
    end_accom = models.OneToOneField(                                                                                                                                                                             
        Accommodation,                                                                                                      
        on_delete=models.CASCADE,                                                                                           
        related_name="accommodation_end"                                                                                                  
    )                                                                                                                       
    mode_of_travel = models.CharField(max_length=50)                                                                        
    description = models.TextField()

Django相关字段的正确使用

Correct Usage of Django Related Fields

sql

django

django-models

django-1.10

python-3.6