Declare NSMutableArray content type

Question

I have a piece of code I've used in an objective c app that I want to incorporate into a new swift project. Problem is I can't work out the syntax!

I'm using FMDB to get some information about sets of cards from a sql database. When I pull the information out of the database I create a card object which has properties described in the database. When I access the database it returns an NSMutableArray of my card objects. I want to explicitly state that my mutable array contains these objects...

I would do this in objective c by writing:

NSMutableArray<Card*>

I'm using it in this context

- (NSMutableArray<Card *> *)getCardsFromDb

So I know my function is returning a mutable array of Card objects. How can I do this in swift?

at the moment the code in my project is minimal

   //Properties
    var cardArray: NSMutableArray<Card>! //How can I tell it that the array is populated with my Card object?

    //View Lifecycle
    override func viewDidLoad() {
        super.viewDidLoad()

        let databaseAccess = DatabaseAccess()

        cardArray = databaseAccess.getCardsFromDatabase()

        print(cardArray)

    }

For the moment I've just called the array a temporary name because I was just testing that the database methods worked. I have tried NSMutableArray[Card] and NSMutableArray(Card) but neither worked.

I would like to do this so that I know when making the database call I am getting an array of card objects, not just some random array.

Thanks

Answer 1

If you want to declare a variable of type array of Card but not save an array into it, you'd use

var cardArray: [Card]

That's equivalent to the Objective-C

NSMutableArray<Card*> cardArray;

(Or rather, the Objective-C is equivalent to the Swift, since Objective-C adopted typed arrays in order to be compatible with Swift.)

If you want to define a variable of type array of Card and put a blank array into it, you'd use

var cardArray = [Card]()

That's equivalent to

NSMutableArray<Card*> cardArray = [NSMutableArray new];

(Although I forget how you satisfy the type requirement in Objective-C. That Objective-C statement might need minor tweaking...)

Answer 2

Since you are writing Swift code, you should declare cardArray as:

var cardArray: [Card] = []

instead of:

var cardArray: NSMutableArray<Card>!

Because getCardsFromDatabase() returns a mutable array (not Swift array), you would need to down cast it first before assign it to cardArray:

override func viewDidLoad() {
    super.viewDidLoad()

    let databaseAccess = DatabaseAccess()

    cardArray = databaseAccess.getCardsFromDatabase() as! [Card]

    print(cardArray)
}