Hi,
I am hoping that there is an easier way of doing this, but I need to
delete individual associations in a many to many relationship without
deleting either of the components (i.e. just the link). The way I
came up with is to use an Association Table and then delete elements
from there.
As below:
class First(Entity):
name = Field(UnicodeText)
thirds = OneToMany('Third')
secondnames = AssociationProxy('thirds', 'second', creator=lambda
second: Third(second=second))
class Second(Entity):
name = Field(UnicodeText)
thirds = OneToMany('Third')
firstnames = AssociationProxy('thirds', 'first', creator=lambda
first: Third(first=first))
class Third(Entity):
first = ManyToOne('First')
second = ManyToOne('Second')
I then pass my reference text to the following function:
def DeleteLink(frst_item, scnd_item):
frst = First.get_by(name=frst_item)
scnd = Second.get_by(name=scnd_item)
thrd = Third.get_by(first=frst,second=scnd)
thrd.delete()
This seems a bit verbose but is fine. However, what happens where I
have a self-referential ManyToMany relationship?
e.g.:
class Fourth(Entity):
name = Field(UnicodeText)
fourth = ManyToMany('Fourth')
How would I delete the link here? I'm not particularly sure how to
code the Association Table and am hoping that there is a way to
achieve this without having to create verbose code.
Help much appreciated, thanks,
Gavin
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