swiftyJSON grab random index from Array

Question

The array contained in the key "children" contains 100 items.

Is there away to tell SwiftyJSON to grab a random index? I tried creating a random number

var random = arc4random_uniform(24)

but when I inserted random I got the error:

"Cannot subscript a value of type 'JSON' with an index of type 'UInt32'"

I also converted it to an NSNumber and same thing, I'm completely lost.

func getBackgoundImageData(completed: @escaping DownloadComplete) {

    let imageURL = URL(string: IMAGE_URL)!
    Alamofire.request(imageURL).responseJSON { response in

        switch response.result {

        case .success(let value):

            let json = JSON(value)
            if let url = json["data"]["children"][0]["data"]["preview"]["images"][0]["source"]["url"].string {
                self._backgroundImageURL = url
            }

        case .failure(let error):
            print(error)
        }
        completed()
    }   
}

In general when you use something like ["data"]["children"][0]["data"]["preview"]["images"][0]["source"]["url"] you are going to have problems as Swift may not be able to infer the types of all those access correctly. Split this line out into a series of conditional downcasts if let data = json["data"] as [String:Any] ... and so on until you get your final array and then use the random index on that — Paulw11
– Paulw11, Commented Dec 1, 2016 at 0:01

Duncan C · Accepted Answer · 2016-12-01 00:33:27Z

1

The arc4random_uniform function's input and returned value are both UInt32. Swift is picky about numeric types, and does not silently convert between them like C family languages do. You should cast random ego an Int:

var random = Int(arc4random_uniform(24))

(And you need to break up your indexing into your data structure as Paul says in his comment.)

answered Dec 1, 2016 at 0:33

Duncan C

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2 Comments

Hurlarious Over a year ago

giddy up! honestly I thought I had attempted to cast it as an Int && NSNumber && pretty much any number format...thanks bud :)

Duncan C Over a year ago

NSNumber is an artifact of the fact that the numeric types are not objects in Objective-C. You can't put numeric values into an NSArray without converting them to NSNumbers. There is no real reason to use NSNumbers in Swift.

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