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Yang Bo
Courses Plus Student 8,503 PointsHow to use Weak or Strong
what's mean Parent-Child relation? Is it for classes relation? for example, if Post has many Reply, so post_id, post_name should be strong in Post, post_id should be weak in Reply. right?
4 Answers
Holger Liesegang
50,595 PointsHi Yang,
yes you're right in as a parent-child relation between instances of objects is meant when trying to avoid a Retain Cycle. A Retain Cycle is the condition when two objects keep a reference to each other and are retained as this creates a retain cycle since both objects try to retain each other, making it impossible to release. You'll have to choose one of the both references and make it a weak pointer (a child so to speak).
... and of course welcome to Treehouse, Yang Bo !
Kind Regards Holger
Holger Liesegang
50,595 PointsYes, exactly - you could think of this like that :) - so if the child has a retain count (ARC) of 0 it will be destroyed (and that will be the case when the last parent - with it's strong pointer to this child - doesn't exist any more). A weak pointer doesn't add to Reference Count.
Holger Liesegang
50,595 Points...editing posts doesn't work as it is supposed to work at the moment...
Yang Bo
Courses Plus Student 8,503 PointsYang Bo
Courses Plus Student 8,503 PointsWow, thank you so much! Holger Liesegang your answer is very helpful and detail. So can I thought it because child is weak pointer to parent, in this way, it is possible to recycle child firstly, and then it is possible to recycling parent after recycled child(parent is't any reference).