class WidgetDC:
__sa_dataclass_metadata_key__ = "sa"
widget_id: int = dataclasses.field(
init=False,
metadata={"sa": Column(Integer, primary_key=True)},
)
# fk on mixin
account_id: int = dataclasses.field(
init=False,
metadata={
"sa":
declared_attr(lambda: Column(
Integer,
ForeignKey("accounts.account_id"),
nullable=False,
))
},
)
has_a_default: str = dataclasses.field(
default="some default",
metadata={"sa": declared_attr(lambda: Column(String(50)))},
)
def _linktable(left_name, right_name, **addtional_columns):
''' Prepare and return a Calibre link table base class.
Parameters:
* `left_name`: the left hand entity, lowercase, singular,
example `'book'`
* `right_name`: the right hand entity, lowercase, singular,
example `'author'`
* `addtional_columns`: other keyword parameters
define further `Column`s and relationships
'''
class linktable(_CalibreTable):
''' Prepare a `_CalibreTable` subclass representing a Calibre link table.
'''
__tablename__ = f'{left_name}s_{right_name}s_link'
setattr(
linktable, f'{left_name}_id',
declared_attr(lambda self: Column(
left_name,
ForeignKey(f'{left_name}s.id'),
primary_key=True,
)))
setattr(
linktable, left_name,
declared_attr(lambda self: relationship(
f'{left_name.title()}s',
back_populates=f'{right_name}_links',
)))
setattr(
linktable, f'{right_name}_id',
declared_attr(lambda self: Column(
right_name,
ForeignKey(f'{right_name}s.id'),
primary_key=True,
)))
setattr(
linktable, right_name,
declared_attr(lambda self: relationship(
f'{right_name.title()}s',
back_populates=f'{left_name}_links',
)))
for colname, colspec in addtional_columns.items():
setattr(
linktable,
colname,
declared_attr(lambda self, colspec=colspec: colspec),
)
return linktable
class AccountDC:
__sa_dataclass_metadata_key__ = "sa"
# relationship on mixin
widgets: List[Widget] = dataclasses.field(
default_factory=list,
metadata={"sa": declared_attr(lambda: relationship("Widget"))},
)
account_id: int = dataclasses.field(
init=False,
metadata={"sa": Column(Integer, primary_key=True)},
)
widget_count: int = dataclasses.field(
init=False,
metadata={
"sa": Column("widget_count", Integer, nullable=False)
},
)
class User:
__tablename__ = "user"
__sa_dataclass_metadata_key__ = "sa"
user_id: int = dataclasses.field(
init=False,
metadata={"sa": Column(Integer, primary_key=True)},
)
# fk w declared attr on mapped class
account_id: int = dataclasses.field(
init=False,
metadata={
"sa":
declared_attr(lambda: Column(
Integer,
ForeignKey("accounts.account_id"),
nullable=False,
))
},
)
