Changes between Initial Version and Version 4 of Ticket #28563


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Timestamp:
Sep 7, 2017, 12:36:13 AM (7 years ago)
Author:
Samuel Spencer
Comment:

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  • Ticket #28563

    • Property Owner changed from nobody to tothegump
    • Property Status new → closed
    • Property Resolution → wontfix

  • Ticket #28563 – Description

    initial v4  
    1 I can't come up with an appropriate example, so I'll use a cut back version of actual code. I'm trying to implement an ISO standard, and am using a concrete base class, with a number of relations between objects, as shown below. Unfortunately, the names of these objects and relations are defined by the spec and can't be changed without a lot of hassle.
    2 
    3 {{{
    4 
    5 class Metadata(models.Model):
    6     name = models.CharField(max_length=255)
    7 
    8 class Property(Metadata):
    9     pass
    10 
    11 class ObjectClass(Metadata):
    12     pass
    13 
    14 class DataElementConcept(Metadata):
    15     object_class = models.ForeignKey(ObjectClass)
    16     property= models.ForeignKey(Property)
    17 
    18 }}}
    19 
    20 However, the system checker has a problem with this:
    21 
    22 {{{
    23 SystemCheckError: System check identified some issues:
    24 
    25 ERRORS:
    26 aristotle_mdr.DataElementConcept.property: (models.E006) The field 'property' clashes with the field 'property' from model 'aristotle_mdr._concept'.
    27 }}}
    28 
    29 What appears to happen is that DataElementConcept.property (a relation between two pieces of metadata) is clashing with MetadataItem.property (a relation from parent class to child class).
    30 
    31 Since a parent-child relationship using inheritance is just a OneToOneField thats made by [https://github.com/django/django/blob/5cc746206726c538c36a2830e7c068f1c8a0e7c8/django/db/models/base.py#L234 django.db.models.base.ModelBase] it'd be nice to be able to add some details to a classes Meta field to change the related_name of the generated field, for example:
    32 
    33 {{{
    34 
    35 class Metadata(models.Model):
    36     name = models.CharField(max_length=255)
    37 
    38 class Property(Metadata):
    39     class Meta:
    40         parent_related_name = "property_subclass"
    41 
    42 }}}
    43 
    44 and the ModelBase coude would be similar to:
    45 
    46 {{{
    47                     field = OneToOneField(
    48                         base,
    49                         on_delete=CASCADE,
    50                         name=attr_name,
    51                         auto_created=True,
    52                         parent_link=True,
    53                         related_name=base._meta.parent_related_name
    54                     )
    55 }}}
     1I didn't even realise that was possible! Cheers.
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