Convert NSArray to Swift Array<T>

Question

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

@NSManaged var types : NSMutableArray

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)Array. How can I type-cast / convert the NSArray to Array<Type>[]?

Apparently the confusion arises from the following error:

let array = obj.types as T[] // Cannot convert expression's type 'Node[]' to type '$T2'

While this is accepted by the editor:

let array = obj.types as AnyObject[] as T[] // No complaint

An ordered relationship is (as far as I know) represented by an NSOrderedSet, not by an NSMutableArray. — Martin R
– Martin R, Commented Jun 26, 2014 at 5:24
"I'm currently using obj.types.allObjects as Type[], but that feels like a hack/workaround". No, that is how you cast an NSArray to a Swift array of a specific type. — matt
– matt, Commented Jun 26, 2014 at 5:36
Wow, why the downvotes? I have the same question and it does seem worthy of asking. — davidethell
– davidethell, Commented Jun 27, 2014 at 19:12

matt · Accepted Answer · 2016-12-03 20:59:22Z

16

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

Then revise your feelings. What you're doing is exactly how you do "type-cast / convert the NSArray to Array<Type>[]."

An NSArray always arrives into Swift as containing AnyObject (i.e. an Array<AnyObject>, aka AnyObject[]). Casting it down to a specific type, if you know that it contains all one type, is up to you, and how you are doing it is exactly what you are supposed to do.

EDIT In Swift 2.0 and the new iOS 9 APIs, an NSArray will often arrive correctly typed, and no cast will be needed.

EDIT 2 In Swift 3.0, an NSArray that is not correctly typed, though uncommon, will arrive as containing Any instead of AnyObject and will still have to be cast down to a specific type.

edited Dec 3, 2016 at 20:59

answered Jun 26, 2014 at 5:37

matt

540k97 gold badges948 silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Bouke Over a year ago

That 'workaround' is not valid for NSArray, but for NSSet. So I'm still looking for a nice solution.

Grady Player Over a year ago

it is valid for an array -allObjects is a method on NSSet that returns all elements as an array.

Bouke Over a year ago

Admitted, I was expecting an allObjects on NSArray; but NSArray itself can be casted to an Array. However I'm still unclear of why two casts are required, see my updated question.

Vivek Gani Over a year ago

Using swift 2.2, the cast is still needed in order to properly use the map function.

Joseph Beuys' Mum · Accepted Answer · 2016-10-28 12:10:56Z

2

The following is a working piece of code from one of my projects that might help?

if let rawArray = rawData as? NSArray,
   let castArray = rawArray as? Array< Dictionary< String, AnyObject > >
   { 
       // etc... 
   }

It works, although I'm not sure it would be considered optimal.

answered Oct 28, 2016 at 12:10

Joseph Beuys' Mum

2,3122 gold badges30 silver badges54 bronze badges

Comments

Vaseltior · Accepted Answer · 2014-09-16 12:13:07Z

1

Enumerate them that way :

for type in types.array {
    // Do something
}

Or use simply the array property of the NSOrderedSet you are using, like so :

types.array

answered Sep 16, 2014 at 12:13

Vaseltior

1,24615 silver badges27 bronze badges

Comments

ColinE · Accepted Answer · 2014-06-26 05:18:42Z

0

You are going to have to create a new generic array and manually populate it as follows:

    var result = Type[]()

    for item : AnyObject in self {
        //  Keep only objC objects compatible with OutType
        if let converted = bridgeFromObjectiveC(item, Type.self) {
            result.append(converted)
        }
    }

answered Jun 26, 2014 at 5:18

ColinE

70.3k16 gold badges171 silver badges236 bronze badges

1 Comment

Bouke Over a year ago

Iterating over an array to copy it to a new array doesn't seem very elegant to me. Is this the most simple solution, even when I know all the instances in the array will be of the same type?

Collectives™ on Stack Overflow

Convert NSArray to Swift Array<T>

4 Answers 4

4 Comments

Comments

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

4 Comments

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related