Update a UILabel using string value from another class in Swift - ios

Question

How do I used a string value from a function in a another class to update an UILabel on my ViewController?
Here is my code:
View controller:
import UIKit
class ViewController: UIViewController, dataEnterdDelegate {
#IBOutlet weak var auaTempLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
let weather2 = WeatherService2()
weather2.getWeatherData("Oranjestad,AW")
}
**func userDidEnterInformation(info: NSString)
{
testLabel!.text = info as String
}**
func setLabel2(information: String)
{
auaTempLabel.text = information
}
The other class named WeatherService2 contain the following codes:
**protocol dataEnterdDelegate{
func userDidEnterInformation(info:NSString)
}**
Class WeatherService2{
var currentTempeture:String?
let targetVC = ViewController()
**var delegate: dataEnterdDelegate?**
func getWeatherData(urlString:String)
{
let url = NSURL(string: urlString)!
let sqlQuery = "select * from weather.forecast where woeid in (select woeid from geo.places(1) where text=\"\(url)\")"
let endpoint = "https://query.yahooapis.com/v1/public/yql?q=\(sqlQuery)&format=json"
let testString = (String(endpoint))
getData(testString)
}
func getData(request_data: String)
{
let requestString:NSString = request_data.stringByAddingPercentEncodingWithAllowedCharacters(NSCharacterSet.URLQueryAllowedCharacterSet())!
let url_with_data = NSURL(string: requestString as String)!
let task = NSURLSession.sharedSession().dataTaskWithURL(url_with_data){
(data, response, error) in dispatch_async(dispatch_get_main_queue(), {
if data == nil
{
print("Failed loading HTTP link")
}else{
self.setLabel(data!)
}
})
}
task.resume()
}
func setLabel(weatherData:NSData)
{
enum JSONErrors: ErrorType
{
case UserError
case jsonError
}
do{
let jsonResults = try NSJSONSerialization.JSONObjectWithData(weatherData, options: .AllowFragments)
if let city = jsonResults["query"] as? NSDictionary
{
if let name = city["results"] as? NSDictionary
{
if let channel = name["channel"] as? NSDictionary
{
if let item = channel["item"] as? NSDictionary
{
if let condition = item["condition"] as? NSDictionary
{
if let temp = condition["temp"] as? String
{
setTemp(temp)
**delegate!.userDidEnterInformation(temp)**
}
}
}
}
}
}
}
catch {
print("Failed to load JSON Object")
}
}
func setTemp(tempeture:String)
{
self.currentTempeture = tempeture
}
func getTemp() ->String
{
return self.currentTempeture!
}
}
The code runs fine and everything but I get an error "Fatal error: unexpectedly found nil while unwrapping an Optional value" when I try to update the UILabel in my ViewController.
When I used the print("The return value is: "+information) in the view controller class it print the return value correctly.
This is the reason I'm confused right now because I don't know why I still getting the "Fatal error: unexpectedly found nil while unwrapping an Optional value" when trying to use this value to update my UILabel.
Can anyone help me with this problem?
Thanks in advance

Answer 1

For that you have to create delegate method.
In viewController you create delegate method and call it from where you get response and set viewController.delegate = self
I could not explain more you have to search for that and it will works 100% .
All the best.

Answer 2

I manage to fix this issue by doing the following:
I create the following class
- Item
- Condition
- Channel
These classes implement the JSONPopulator protocol.
The JSONPopulator protocol:
protocol JSONPopulator
{
func populate(data:AnyObject)
}
Item class:
class Item: JSONPopulator
{
var condition:Condition?
func getCondition() ->Condition
{
return condition!
}
func populate(data: AnyObject)
{
condition = Condition()
condition?.populate(data)
}
}
Condition class:
class Condition:JSONPopulator
{
var arubaTemp:String?
var channel:NSDictionary!
func getArubaTemp()->String
{
return arubaTemp!
}
func getBonaireTemp() ->String
{
return bonaireTemp!
}
func getCuracaoTemp()->String
{
return curacaoTemp!
}
func populate(data: AnyObject)
{
if let query = data["query"] as? NSDictionary
{
if let results = query["results"] as? NSDictionary
{
if let channel = results["channel"] as? NSDictionary
{
self.channel = channel
if let location = channel["location"] as? NSDictionary
{
if let city = location["city"] as? String
{
if city.containsString("Oranjestad")
{
switch city
{
case "Oranjestad":
arubaTemp = getTemp()
print(arubaTemp)
default:
break
}
}
}
}
}
}
}
}
func getTemp() ->String
{
var temp:String?
if let item = self.channel["item"] as? NSDictionary
{
if let condition = item["condition"] as? NSDictionary
{
if let tempeture = condition["temp"] as? String
{
print(tempeture)
temp = tempeture
}
}
}
print(temp)
return temp!
}
}
Channel class:
class Channel: JSONPopulator
{
var item:Item?
var unit:Unit?
var request_city:String?
func setRequestCity(request_city:String)
{
self.request_city = request_city
}
func getRequestCity() ->String
{
return request_city!
}
func getItem() -> Item
{
return item!
}
func getUnit() -> Unit
{
return unit!
}
func populate(data: AnyObject)
{
item = Item()
item?.populate(data)
}
}
The WeatherService class that handles the function of parsing the JSON object. This class implement a WeatherServiceCallBack protocol.
The WeatherServiceCallBack protocol:
protocol WeatherServiceCallBack
{
func arubaWeatherServiceService( channel:Channel)
func arubaWeatherServiceFailure()
}
WeatherService class:
class WeatherService
{
var weatherServiceCallBack:WeatherServiceCallBack
var requestCity:String?
init(weatherServiceCallBack: WeatherServiceCallBack)
{
self.weatherServiceCallBack = weatherServiceCallBack
}
internal func checkCity(city:String)
{
switch (city)
{
case "Oranjestad,AW":
requestCity = city
getWeatherData(requestCity!)
default:
break
}
}
func getWeatherData(urlString:String)
{
let url = NSURL(string: urlString)!
let sqlQuery = "select * from weather.forecast where woeid in (select woeid from geo.places(1) where text=\"\(url)\")"
let endpoint = "https://query.yahooapis.com/v1/public/yql?q=\(sqlQuery)&format=json"
let testString = (String(endpoint)
executeTask(testString)
}
func executeTask(request_data: String)
{
let requestString:NSString = request_data.stringByAddingPercentEncodingWithAllowedCharacters(NSCharacterSet.URLQueryAllowedCharacterSet())!
let url_with_data = NSURL(string: requestString as String)!
let task = NSURLSession.sharedSession().dataTaskWithURL(url_with_data){
(data, response, error) in dispatch_async(dispatch_get_main_queue(), {
if data == nil
{
print("Failed loading HTTP link")
}else{
self.onPost(data!)
}
})
}
task.resume()
}
func onPost(data:NSData)
{
enum JSONErrors: ErrorType
{
case UserError
case jsonError
}
do{
let jsonResults = try NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments)
print(jsonResults)
if let city = jsonResults["query"] as? NSDictionary
{
if let name = city["count"] as? Int
{
if name == 0
{
weatherServiceCallBack.arubaWeatherServiceFailure()
}
}
}
if let requestCity_check = jsonResults["query"] as? NSDictionary
{
if let results = requestCity_check["results"] as? NSDictionary
{
if let channel = results["channel"] as? NSDictionary
{
if let location = channel["location"] as? NSDictionary
{
if let city = location["city"] as? String
{
requestCity = city
let channel = Channel()
channel.setRequestCity(requestCity!)
channel.populate(jsonResults)
weatherServiceCallBack.arubaWeatherServiceService(channel)
}
}
}
}
}
}catch {
print("Failed to load JSON Object")
}
}
}
In the ViewController class (I add some animation to the UILabel so it can flip from Fahrenheit to Celsius):
class ViewController: UIViewController, WeatherServiceCallBack
{
var weather:WeatherService?
var aua_Tempeture_in_F:String?
var aua_Tempeture_in_C:String?
var timer = NSTimer()
#IBOutlet var aua_Temp_Label: UILabel!
let animationDuration: NSTimeInterval = 0.35
let switchingInterval: NSTimeInterval = 5 //10
override func viewDidLoad() {
super.viewDidLoad()
weather = WeatherService(weatherServiceCallBack: self)
weather?.checkCity("Oranjestad,AW")
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func animateTemptext()
{
self.timer = NSTimer.scheduledTimerWithTimeInterval(7.0, target: self, selector: Selector("tempConvertionTextSwitch"), userInfo: nil, repeats: true)
}
func setTempinCelsius(temp_string:String)
{
aua_Tempeture_in_F = "\(temp_string)°F"
let convertedString = convertFahrenheittoCelsius(temp_string)
aua_Tempeture_in_C = "\(convertedString)°C"
aua_Temp_Label.text = aua_Tempeture_in_C
animateTemptext()
}
func convertFahrenheittoCelsius(currentTemp:String) ->String
{
let tempTocelsius = (String(((Int(currentTemp)! - 32) * 5)/9))
return tempTocelsius
}
#objc func tempConvertionTextSwitch()
{
CATransaction.begin()
CATransaction.setAnimationDuration(animationDuration)
CATransaction.setCompletionBlock{
let delay = dispatch_time(DISPATCH_TIME_NOW,Int64(self.switchingInterval * NSTimeInterval(NSEC_PER_SEC)))
dispatch_after(delay, dispatch_get_main_queue())
{
}
}
let transition = CATransition()
transition.type = kCATransitionFade
if aua_Temp_Label.text == aua_Tempeture_in_F
{
aua_Temp_Label.text = aua_Tempeture_in_C
}else if aua_Temp_Label.text == aua_Tempeture_in_C
{
aua_Temp_Label.text = aua_Tempeture_in_F
}else if aua_Temp_Label == ""
{
aua_Temp_Label.text = aua_Tempeture_in_C
}
aua_Temp_Label.layer.addAnimation(transition, forKey: kCATransition)
CATransaction.commit()
}
func arubaWeatherServiceFailure() {
}
func arubaWeatherServiceService(channel: Channel)
{
let requested_city = channel.getRequestCity()
let items = channel.getItem()
let aua_Temp = items.getCondition().getArubaTemp()
setTempinCelsius(aua_Temp)
}
}
Reference:
iOS 8 Swift Programming Cookbook Solutions Examples for iOS Apps book
iOS 8 Programming Fundamentals with Swift Swift, Xcode, and Cocoa Basics book
Hope it help the once that had the same problem