如何使用另一个类中的函数的字符串值来更新ViewController上的UILabel？ 这是我的代码：
查看控制器：
导入UIKit
类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
}
另一个名为WeatherService2的类包含以下代码：
**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!
}
}
代码运行正常，但是当我尝试更新ViewController中的UILabel时，我收到错误“致命错误：在展开可选值时意外发现nil”。
当我在视图控制器类中使用print("The return value is: "+information)时，它会正确打印返回值。
这就是我现在感到困惑的原因，因为我不知道为什么我仍然会在尝试使用此值来更新我的UILabel时遇到“致命错误：在展开可选值时意外发现nil”。
任何人都可以帮我解决这个问题吗？
提前致谢
答案 0 :(得分：0)
为此你必须创建委托方法。
在viewController中，您可以创建委托方法并从获得响应的位置调用它并设置viewController.delegate = self
我无法解释更多你必须搜索它，它将100％工作。
一切顺利。
答案 1 :(得分：0)
我设法通过执行以下操作来解决此问题： 我创建了以下类 - 项目 - 条件 - 频道 这些类实现 JSONPopulator 协议。 JSONPopulator 协议：
protocol JSONPopulator
{
func populate(data:AnyObject)
}
项目类：
class Item: JSONPopulator
{
var condition:Condition?
func getCondition() ->Condition
{
return condition!
}
func populate(data: AnyObject)
{
condition = Condition()
condition?.populate(data)
}
}
条件类：
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!
}
}
频道类：
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)
}
}
WeatherService 类，用于处理解析JSON对象的功能。该类实现了 WeatherServiceCallBack 协议。 WeatherServiceCallBack 协议：
protocol WeatherServiceCallBack
{
func arubaWeatherServiceService( channel:Channel)
func arubaWeatherServiceFailure()
}
WeatherService 类：
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")
}
}
}
在 ViewController 类中（我向UILabel添加了一些动画，以便它可以从华氏温度转换为摄氏温度）：
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)
}
}
参考：
iOS 8 Swift编程手册iOS应用程序解决方案示例书
使用Swift Swift，Xcode和Cocoa Basics的iOS 8编程基础书
希望它有助于曾经遇到同样问题的人