Hi,
Suppose I have the following ORM class:
class User(Base):
__tablename__= 'users'
first_name = Column(String(64), nullable=False)
last_name = Column(String(64), nullable=False)
email = Column(String(128), nullable=False)
In our project we now need the full name of a User, as well as her long
email address (and other data derived from the ORM’s mapped/stored data).
There are two ways to implement this:
1. Add @property to the User object.
2. Add helper functions to a utility module.
The discussion is now going forth and back between these two approaches.
One view is to use @property for the User class:
@property
def name(self):
return self.first_name + " " + self.last_name
@property
def long_email(self):
return "{0} <{1}>".format(self.name, self.email)
because semantically these properties “belong” to a user, keep other scopes
clean by avoiding unnecessary imports, and they are stateless and
read-only, and do not affect the underlying data. (Even if they did, the
ORM should then handle these state changes consistently: e.g. assigning a
full name to a User object.)
The other view is to use helper functions:
from orm.model import User
def get_name(user: User) -> str:
return user.first_name + " " + user.last_name
def get_email(user: User) -> str:
return "{0} <{1}>".format(self.name, self.email)
because @property add responsibility to the User object and an ORM should
not *create* new data based from its model.
So… what are the opinions of the wider audience here? 🙃
Cheers,
Jens
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