Should i use Cascade or nullify in Core Data for a relationship?

Question

I have a one-to-many relationship and I am just trying to get a few things straight. When I set the relationship from A <-->> B everything is great and works out just the way I like. But when I want to change the relationship, clear everything out and add a couple different B's (than I did before), would I delete the relationship using nullify or cascade if I wanted it to be removed on both ends?

Also could any one give me a quick example of how I might go about this?

I was thinking something like [b setValue:nil forKey:myRelationship]

Is that anywhere close? Or do I need something else?

Thanks.

Answer 1

These relationship types apply when deleting managed objects themselves, not clearing out the relationships. So, if you have object 'a' linked to 'b', 'c', and 'd', then when you delete 'a':

• if the relationship is 'cascade', 'b', 'c', and 'd' will all be deleted as well
• if it's 'nullify', then just the relationship back to 'a' will be cleared on these objects.

In all cases, you can use [b setValue: nil for Key: myRelationship] to clear out the relationship on both sides.