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core-dataswift3magicalrecord

Sort model array as per date which is present in another model array. Swift 3

I am having a model array say [Conversation].

In the conversation model object there is another model array say [Message].

In Message model object there is a property say createdOn

So I am trying to sort conversation array in descending order as per property createdOn (a Date property) which is in Message model.

I have sorted Message array successfully. but I am having no luck in sorting conversation array.

let msgArray = Message.mr_findAll() as? [Message]
let sortDescriptor = NSSortDescriptor(key: "createdOn", ascending: false)
let orderedArray = (msgArray as? NSArray)?.sortedArray(using: [sortDescriptor]) as! [Message]

P.S.

I am using Magical records for database.

Solution

  • I assume that a conversation has many messages and that you want to sort it by the last message sent like most chat app do. If that is the case, I would recommend storing the last updated date in the conversation object and updating it whenever a message is inserted.