Convert NSSet to Swift Array

Question

In CoreData I have defined an unordered to-many relationship. This relationship is defined in Swift like this:

@NSManaged var types : NSMutableSet

However, to use Swift at it's best, I want to use a normal Swift array like Type[]. However, CoreData forces me to use NS(Mutable)Set. How can I type-cast / convert the NSSet to Array<Type>[]?

Kine

possible duplicate of Convert NSArray to Swift array – Boffin

Type-cast is not possible since NSSet doesn't inherit NSArray, but you can convert to NSArray with types.allObjects() – Monster

@Boffin it's not a duplicate as the one you're referring to is about NSArray and this is about NSSet. Different types, different question and probably different answers. – Kine

yes, that is duplicate, because the NSSet can be converted NSArray and the solution is the same from that point. – Florist

@holex, well actually that's not true either. NSSet can be converted to an Array, as shown in the answers below. However NSArray doesn't appear to have an 'easy' cast / convert to Array. – Kine

@bouke, the Swift documentation says the following about Cocoa Types: Swift automatically bridges between the Array type and the NSArray class., and (...)in Swift code, you can pass an Array value to a method expecting an NSArray object. You can also cast between a bridged type and its counterpart., I guess that is quite clear statement, source: developer.apple.com/library/prerelease/mac/documentation/Swift/…, and you are welcome! – Florist

Answer 1

As of Xcode 7.2 with Swift 2.1.1

Actually, I found out by trial that:

@NSManaged var types : Set<Type>

Works perfectly fine.

The fact is that CoreData generates somethink like:

@NSManaged var types : NSSet

when creating a NSManagedObject subclass from the editor. So I was wondering if there was a not very verbose method to use the filter method without casting. But then Swift is supposed to bridge automatically between NSSet, NSArray and their counterparts. So I tried declaring it directly as a Set and it works.

Answering the question, converting it to an Array becomes trivial:

Array(types)

Lindo

Core Data uses NSSet to optimise things under the hood. It might be less memory efficient to use Set even though the ergonomic is better. – Wommera

Answer 2

var set = NSSet() //NSSet
var arr = set.allObjects //Swift Array
var nsarr = set.allObjects as NSArray  //NSArray

Frankly

While this answer is still valid, Swift 1.2 now also contains a native Set structure. The Set doesn't have allObjects, but supports (most) operations that an array would support. So there is less need to convert a NSSet to array. – Kine

This really helped me with my collectionview - I used it to allow my CoreData NSSet to drive my collectionView via indexpath.row – Tigerish

To expand on the comment @bouke posted, you can convert a Swift Set to Array like let array = Array(mySet) – Lianeliang

Answer 3

This is how I did it:

let array = object.NSSet?.allObjects as! [ArrayType]

Then you can manipulate the array as normal:

for item in array {
    id = item.id
}

Pedestal

Answer 4

Use map to get array like this:

extension NSSet {
  func toArray<T>() -> [T] {
    let array = self.map({ $0 as! T})
    return array
  }
}

...
let myArray: [MyType] = set.toArray()

Evadnee

Answer 5

This answer is outdated as of Xcode 7.2/Swift 2.1. See the accepted answer for an updated answer.

---

I'm currently using obj.types.allObjects as Type[], but that feels like a hack/workaround.

Kine

It's alright man, in Swift 1.2 a native Set will be introduced so a workaround is fine at the time being. – Marucci

As of Xcode 7, Swift 2. CoreData stil uses NSSet, so this very set till needs to be turned into either a native Array or native Set. – Silkweed

@Silkweed Actually, as of Xcode 7.2 (I haven't tried other versions), it works if you declare it directly as a native Set as I explain in my answer. – Lindo

Thanks for the details. +1. You may want to be specific about Xcode version in your answer. – Silkweed

Answer 6

You can also use .sortedArray to sort the elements.

Swift 3:

yourNSSetType?.sortedArray(using: [NSSortDescriptor(key: "keyToSortBy", ascending: true, selector: #selector(NSNumber.compare(_:)))]) as! [yourNSSetType]

For strings, use NSString.compare in the #selector call.

Immoral

Answer 7

Thanks to @David for his solution I had the same situation In my current project, we still use Objective C with swift bridging for the coredata modules so in my case, I had to use the following as compiler can't intervene what is the Generic Type to convert i had to pass it with using actually :(

extension Set {
    
    func toArray<S>(_ of: S.Type) -> [S] {
        let array = self.map({$0 as! S})
        return array
    }
    
}

and using:

Items?.toArray(XYZ.self)

in my Managed object; variable was like this for reference

@property (nullable, nonatomic, retain) NSSet<XYZ *> * items;

Sequester

Answer 8

Here's how to do it with a ForEach view in SwiftUI

ForEach(object.allObjects as! [ObjectType], id: \.self)
{ obj in
    Text("\(obj.name)")
}

XCode 14.2, targeting iOS 16.2

Ruckus