How to append an empty value to NSData Array (Swift)

Question

I have

var images: [NSData] = [];

and I need to add empty values into this array during executing of my for-loop block and then replace these empty values on NSData of the images I downloaded from the server.

How should I append an empty value to NSData-array?

I tried some like ... as! NSData ... as! NSData , or create variable someVar: NSData? - app crashes every time

Answer 1

Create an empty Data ( NSData in Swift 2) instance and append it to the array

var images: [Data] = []
let emptyData = Data()
images.append(emptyData)

Answer 2

Make an array of optionals var images: [NSData?] = [];
And add nil values when in for-loop images.append(nil)
After that replace with your real data if you know position in array

Answer 3

You could have your array be optional NSData like so:

var images: [NSData?] = [];

That way, you can set nil if you want:

images.append(nil)

And check on the loop:

for imageData in images {
    if let data = imageData {
        // data exists
    } else {
        // data doesn't exist yet at this index
    }
}