Swift JSON Parsing Avoid method declaration for every view - ios

Question

I'm working on fetching data from json and manipulating it into a table view, but the problem is that I have many views, about 5-6 and in each one with separate class, and in each class I declare the same JSON Parsing method again and again, how can I avoid such repetition? I wanted to declare the method as class method in AppDelegate, but I ran into a problem:
After the return of json, I would use it in another function to extract the data, But I'm stuck over here with this error. Please help! If there's a better approach I would like to know.
Thank you
UPDATE
class func get_data_from_url(url:String) -> NSString
{
var json:NSString?
let url = NSURL(string: url)
let urlRequest = NSMutableURLRequest(URL: url!,
cachePolicy: .ReloadIgnoringLocalAndRemoteCacheData,
timeoutInterval: 15.0)
let queue = NSOperationQueue()
NSURLConnection.sendAsynchronousRequest(
urlRequest,
queue: queue,
completionHandler: {(response: NSURLResponse!,
data: NSData!,
error: NSError!) in
if data == nil {
dispatch_async(dispatch_get_main_queue(), {
let alert = UIAlertView()
alert.title = "Connection Error"
alert.message = "Could not connect to the server"
alert.addButtonWithTitle("Ok")
alert.show()
});
}
else {
if data.length > 0 && error == nil{
json = NSString(data: data, encoding: NSASCIIStringEncoding)
}else if data.length == 0 && error == nil{
println("Nothing was downloaded")
return
} else if error != nil{
println("Error happened = \(error)")
return
}
}
}
)
return json!
}
I'm getting an error at the last line, "return json!" -> "fatal error: unexpectedly found nil while unwrapping an Optional value"
Any Suggestions?

Answer 1

Try something like this : your ClassB is where you load the json, so from Class A, you call the method loadJson, and when the json has been downloaded in Class B, you send the json back to Class A :
//Class A :
ClassB.loadJson{ (success, json) -> Void in
if (success) //... you use the json
//println("receive json from Class B, use it here")
return
}
//ClassB
typealias OnComplete = (Bool, NSString) -> ()
class func loadJson(completion:OnComplete){
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), { () -> Void in
//json = ... load your json here
dispatch_async(dispatch_get_main_queue(), { () -> Void in
println("json loaded")
completion(true, json) //send result back to Class A
})//main
}