NSJSONSerialization no returns error

Question

There code:

var err: NSError
var jsonDict = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: &err) as Array<NSDictionary>

If data has JSON it's works perfect. But if there something other (not JSON Array) it's just has fatal error and iOS simulator close with EXC_BAD_INSTRUCTION. So there no call err. How I can check data before? Or catch the error.

Answer 1

(Sorry, am in a hurry, no description yet.)

    var err: NSError?
    var jsonDict: AnyObject!
    var data: AnyObject = "{ }".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)
    if let d = data as? NSData {
        jsonDict = NSJSONSerialization.JSONObjectWithData(d, options: NSJSONReadingOptions.MutableContainers, error: &err)
        if let dict = jsonDict as? NSDictionary {
            // Do something with `dict`
            println(dict)
        }
    }