Converting Set to Array?

Question

When retrieving a collection of objects from CoreData via a relationship, swift is giving me an NSSet rather than an array as i would have expected.

Is there a way i can convert the set into an array?

Code:

var updateExercise : UserExercise?

destinationViewController?.userExerciseSets = self.updateExercise?.exercisesets as? [UserExerciseSet]

the cautions are

Cast from 'NSSet?' to unrelated type '[UserExerciseSet]' always fails

Destination VC has the var : var userExerciseSets : [UserExerciseSet]?

jimj · Accepted Answer · 2017-03-12 17:16:26Z

11

You should define your NSManagedObject model as such:

class UserExercise: NSManagedObject {
   @NSManaged var exercises: Set<Exercise>!
}

Then when you need an array, you can simply use the Array's constructor that takes a set.

let exercises = Array(userExercise.exercises)

edited Mar 12, 2017 at 17:16

answered Mar 12, 2017 at 17:08

jimj

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2 Comments

Grimxn Over a year ago

Indeed, but remember that it's a set for a reason - there is no guarantee of order, and two calls to Array() with the same Set may not return elements ordered the same way...

jimj Over a year ago

Correct, there should also be an explicit sort in addition to this if it's used for display in the UI. Good catch.

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