Geek Answers Handbook

How to override hash and isEqual for NSManagedObjects?

We have a group of NSManagedObjects of various types. Some of them have NSSet members of other NSManagedObjects. The problem is that I really need to override the hash methods and isEquals of the objects in the set, but they are NSManagedObjects. I'm having trouble getting multiple identical objects in a set. As far as I can tell, since the hash by default corresponds to the address of the object - all objects are different. Therefore, I need to override the hash and isEquals, but I see no way to do this.

We have a bunch of things in the System, and more comes through XML - sometimes existing objects are repeated. When they match, I do not want doublets to be added to the set.

+4
source share
1 answer

As Wain mentioned above, the NSManagedObject Documentation states that you should not override hash or isEqual: Thus, this means that the stock NSSet not doing what you need.

Some of your options are:

  • Enumerate NSSet content to identify and remove duplicates
  • Write a factory method for your NSManagedObjects that will return the same object when providing the same data
  • Correct XML to not include duplicate objects
  • Unique objects originating from XML before they become NSManagedObjects
  • Modify the input XML to include a unique identifier that you can track, provided that the duplicated objects are exact duplicates.
  • Implement your own data collection class, similar to NSSet, which performs a different unique test than hash and isEqual:
0
source

More articles:


All Articles