In Swift 2, how to cast a JSON array to [Int32]

Question

I have the following code to read in a JSON file and then cast its arrays to either [Float32] or [Int32]

let location = NSString(string:"/Users/myname/Documents/test.js").stringByExpandingTildeInPath
let rawData = NSData(contentsOfFile: location)
let modelData = try? NSJSONSerialization.JSONObjectWithData(rawData!, options: NSJSONReadingOptions.AllowFragments)

let dict = modelData as! NSDictionary
guard let vertices = dict["vertices"] as? [Float32] else {
    print("error casting vertices")
    return
}
guard let indices = dict["faces"] as? [Int32] else {
    print("error casting indices")
    return
}

The contents of the JSON file is:

{
    "vertices" : [1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9],
    "faces" : [0,1,2]
}

The JSON file has been loaded and parsed successfully, however, the cast of vertices to [Float32] succeeds while the cast of faces to [Int32] fails. Is there anyway to cast faces to [Int32]?

gasho · Answer 1 · 2016-02-04T07:37:55.847

2

Just cast it to [Int] not [Int32]. You can check the type like so

dict["faces"] is [Int]

edited Feb 04 '16 at 07:37

answered Feb 04 '16 at 07:17

gasho

1,926
1
16
20

Just for reference, what's the difference between Int and Int32? – Joachim Isaksson Feb 04 '16 at 07:46
This guy explained it well [here](http://stackoverflow.com/questions/27440100/what-is-the-difference-between-int-and-int32-in-swift#answer-27440158) – gasho Feb 04 '16 at 07:53
Something else I would suggest is to use swift's dictionary - [String: AnyObject] – gasho Feb 04 '16 at 07:59

score 1 · Accepted Answer · answered Feb 04 '16 at 07:47

1

When you do let indices = dict["faces"] indices array is created of type Array<Double> thus you can not type cast it as [Int32] or even as [Int]. You can try out following code to convert it to [Int32]

let faces = dict["faces"]! as [AnyObject]
let intFaces = (faces as! [Int]).map({Int32($0)})

intFaces will be of type [Int32]

answered Feb 04 '16 at 07:47

Vishnu gondlekar

3,896
21
35

1

looks like the first line of code should be `let faces = dict["faces"] as? [AnyObject]` in Swift 2 – shapeare Feb 04 '16 at 07:53

In Swift 2, how to cast a JSON array to [Int32]

2 Answers2