Swift Errors Thrown from here are not handled - json

Question

I have had my code working in Xcode 6 but since I got Xcode 7 I cannot figure out how to fix this. The let jsonresult line has an error that says Error thrown from here are not handled. Code is below:
func connectionDidFinishLoading(connection: NSURLConnection!) {
let jsonresult:NSDictionary = try NSJSONSerialization.JSONObjectWithData(self.bytes, options: NSJSONReadingOptions.MutableContainers) as! NSDictionary
print(jsonresult)
let number:Int = jsonresult["count"] as! Int
print(number)
numberElements = number
let results: NSDictionary = jsonresult["results"] as! NSDictionary
let collection1: NSArray = results["collection1"] as! NSArray
Thanks

Answer 1

If you look at the definition of JSONObjectWithData method in swift 2 it throws error.
class func JSONObjectWithData(data: NSData, options opt: NSJSONReadingOptions) throws -> AnyObject
In swift 2 if some function throws an error you have to handle it with do-try-catch block
Here is how it works
func connectionDidFinishLoading(connection: NSURLConnection!) {
do {
let jsonresult:NSDictionary = try NSJSONSerialization.JSONObjectWithData(self.bytes, options: NSJSONReadingOptions.MutableContainers) as! NSDictionary
print(jsonresult)
let number:Int = jsonresult["count"] as! Int
print(number)
numberElements = number
let results: NSDictionary = jsonresult["results"] as! NSDictionary
let collection1: NSArray = results["collection1"] as! NSArray
} catch {
// handle error
}
}
Or if you don't want handle error you can force it with try! keyword.
let jsonresult:NSDictionary = try! NSJSONSerialization.JSONObjectWithData(self.bytes, options: NSJSONReadingOptions.MutableContainers) as! NSDictionary
print(jsonresult)
As with other keywords that ends ! this is a risky operation. If there is an error your program will crash.