Hi,
I have a mixin like:
class BasicSqlClass(object):
@declared_attr
def __tablename__(cls):
return convert(cls.__name__) + 's
The mixin declares the table name and does other stuff.
Hover, there is a class where I wanted to overwrite the mixed-in
__tablename__ by declaring the __tablename__ for the class like.
class SpecialClass(BasicSqlClass, db.Model):
__tablename__ = 'other_table_name'
However, that didn't work. the mixed-in __tablename__ was still used. I
also tried writing a declared attribute for the SpecialClass, but that
didn't overwrite the mixin either.
class SpecialClass(BasicSqlClass, db.Model):
@declared_attr
def __tablename__(cls):
return 'other_table_name'
I ended up making a special mixin to overwrite the __tablename__.
class OverwriteTableName(object):
#I needed to make a class to overwrite the table name
__tablename__ = 'other_table_name'
class SpecialClass(OverwriteTableName, BasicSqlClass, db.Model):
The special mixin worked, though I was surprised I was not able to
overwrite the mixed-in __tablename__ like a regular inherited attribute.
Any thoughts on this? If the behavior is expected or intended, If perhaps
a warning about this behavior could be added to the documentation that
would be great. I've written a comment below, but I don't know how to
propose it's addition to the documentation.
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">
Mixed-In declared attributes can only be overridden by other mixins. A
declared attribute inherited from a mixed-in class cannot be overridden
directly. For example, a class has a __tablename__ attribute inherited
from a mixin where __tablename__ is defined as a declared attribute. Just
adding __tablename__ to the class is insufficient to overwrite the
__tablename__ inherited from the mixin for the class. A second mixin with
the __tablename__ attribute must be declared and added to the class with
inheritance priority over the mixin.
</p>
</div>
I'm thinking it would go at:
https://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/mixins.html
https://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/api.html#sqlalchemy.ext.declarative.declared_attr
Thanks!
~Victor
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