Hi, I have 3 classes: two have many to many relationship between them, one
is association class.
class Person:
...
tools = relationship('Association', back_populates='user', lazy=True,
cascade='all, delete-orphan')
class Tool:
...
users = relationship('Association', back_populates='tool', lazy=True,
cascade='all, delete-orphan')
One person object has 3 tools [<Tool id=1>, <Tool id=2>, <Tool id=3>]. When
I update the tool of the person I did
person.tools = []
for tool_id in [2, 4, 5]:
tool = Tool.query.get(tool_id)
if tool:
person.tools.append(tool)
This operation fails, since when I set tools to an empty list, tool 1,2,3
are deleted, so only tool 4,5 are added into the list. If I remove the
delete-orphan in the cascade, I will have some redundant data in the
database. I can remove the unwanted tools from person.tools first instead
of setting it to empty list. I'd like to know if there is a simple way to
achieve same result. Thank you.
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