On Mar 10, 2008, at 9:19 AM, Christophe Alexandre wrote:
> Hi,
>
> Assuming you have a one-to-many type of relationship, say one user
> has several roles.
>
> The underlying "role" table would hold one foreign key referring to
> the user table.
>
> A properly written SA ORM allows you to write:
>
> user1.roles
>
> Now assuming you have just created a new user (user2), what is the
> easiest way if you want to "copy" roles from user1?
>
> I tried:
>
> user2.roles = user1.roles
>
> But then it deletes the roles from user1.
my first impression is that a relation from "users" to "roles" is
typically a many to many. That you are looking to have the same roles
present on more than one user implies this as well. But we can still
work with one-to-many.
> Same if I go through a copy.copy():
>
> import copy
> user2.roles = copy.copy(user1.roles)
copy is going to fail because its copying the full state of each user,
including the primary key, instance key, and probably the _state which
is putting your session into an invalid state.
>
> Does anyone have an idea? I would like to avoid going through a loop
> and creating the roles one by one.
First I'd put a convenience method on Role to handle generating a new
Role object with the same value:
def asnew(self):
return Role(self.name, ...)
then I'd just use a list comprehension to make the copy:
user2.roles = [r.asnew() for r in user.roles]
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