I am following an e-class tutorial for SWIFT // XCODE 11.4 and I have to fetch data from Open Weather API and display it on the interface where people can type in a city and the view controller will display temperature, cloud icon, and description.
I am using the MVC pattern design and the delegate design to accomplish this tutorial. My swift files are as followed:
Swift Files in MVC Design Pattern
Here are the codes in each of the important files:
I. Model folder
WeatherManager.swift
protocol WeatherManagerDelegate {
func didUpdateWeather(weather: WeatherModel)
}
struct WeatherManager {
let weatherURL = "https://api.openweathermap.org/d.5/weather?appid=c8b50079338280b47a65dd6082551e3b&units=imperial"
let delegate: WeatherManagerDelegate?
func fetchWeather(cityName: String) {
let urlString = "\(weatherURL)&q=\(cityName)"
performRequest(urlString: urlString)
}
func performRequest(urlString: String) {
//create a URL
if let url = URL(string: urlString) {
//create a URLSession
let session = URLSession(configuration: .default)
//give session a task
let task = session.dataTask(with: url) { (data, response, error) in
if error != nil {
print(error!)
return //exit out of the func if there is an error
}
if let safeData = data {
if let weather = self.parseJSON(weatherData: safeData) {
self.delegate?.didUpdateWeather(weather: weather)
}
}
}
//start the tast
task.resume()
}
}
func parseJSON (weatherData: Data) -> WeatherModel? {
let decoder = JSONDecoder()
do {
let decodedData = try decoder.decode(WeatherData.self, from: weatherData)
let id = decodedData.weather[0].id
let temp = decodedData.main.temp
let name = decodedData.name
let weather = WeatherModel(conditionId: id, cityName: name, temperature: temp)
return weather
} catch {
print(error)
return nil
}
}
}
WeatherData.swift
struct WeatherData: Codable {
let name: String
let main: Main
let weather: [Weather]
}
struct Main: Codable {
let temp: Double
}
struct Weather: Codable {
let id: Int
}
WeatherModel.swift
struct WeatherModel {
let conditionId: Int
let cityName: String
let temperature: Double
var temperatureString: String {
return String(format: "%.1f", temperature)
}
var conditionName: String {
switch conditionId {
case 200...232:
return "cloud.bolt"
case 300...321:
return "cloud.drizzle"
case 500...531:
return "cloud.rain"
case 600...622:
return "cloud.snow"
case 701...781:
return "cloud.fog"
case 800:
return "sun.max"
case 801...804:
return "cloud.bolt"
default:
return "cloud"
}
}
}
II. Controller
WeatherViewController.swift (place where the error is)
class WeatherViewController: UIViewController, UITextFieldDelegate, WeatherManagerDelegate {
@IBOutlet weak var conditionImageView: UIImageView!
@IBOutlet weak var temperatureLabel: UILabel!
@IBOutlet weak var cityLabel: UILabel!
@IBOutlet weak var searchTextField: UITextField!
var weatherManager = WeatherManager()
override func viewDidLoad() {
super.viewDidLoad()
weatherManager.delegate = self
searchTextField.delegate = self
}
@IBAction func searchPressed(_ sender: UIButton) {
searchTextField.endEditing(true)
}
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
searchTextField.endEditing(true)
print(searchTextField.text!)
return true
}
func textFieldShouldEndEditing(_ textField: UITextField) -> Bool {
if textField.text != "" {
return true
} else {
textField.placeholder = "Type something..."
return false
}
}
func textFieldDidEndEditing(_ textField: UITextField) {
if let city = searchTextField.text {
weatherManager.fetchWeather(cityname: city)
}
searchTextField.text = ""
}
func didUpdateWeather(weather: WeatherModel) {
print(weather.temperature)
}
}
Here is the error message: Missing argument for parameter 'delegate' in call Error message in WeatherViewControl.swift
And when I hit the run button, I also got this error in the debug console:
dataCorrupted(Swift.DecodingError.Context(codingPath: [], debugDescription: "The given data was not valid JSON.", underlyingError: Optional(Error Domain=NSCocoaErrorDomain Code=3840 "Invalid value around character 0." UserInfo={NSDebugDescription=Invalid value around character 0.})))
What should I do to get rid of these errors?
Missing argument for parameter 'delegate' in call
When a struct is create a value for each property is required.
If each property is specified with a default value and there is no user-defined initializer then Swift will create a default initializer for the struct.
If there is at least one property without a default value and there is no user-defined initializer then Swift will create a memberwise initializer which has one parameter for each property without a default value.
For example your type:
struct WeatherModel {
let conditionId: Int
let cityName: String
let temperature: Double
...
has three properties without default values. If you start typing:
let myWeatherModel = WeatherModel(
and then take the completion offered you will get (something like):
let wm = WeatherModel(conditionId: <Int>, cityName: <String>, temperature: <Double>)
The completion is showing the memberwise initializer.
Your type which produces the error is:
struct WeatherManager {
let weatherURL = "https://api.openweathermap.org/d.5/weather?appid=c8b50079338280b47a65dd6082551e3b&units=imperial"
let delegate: WeatherManagerDelegate?
which has two properties only one of which has a default value, and it has no initializers, so Swift will create a member wise initialiser automatically.
There is nothing wrong so far.
The line producing the error is:
var weatherManager = WeatherManager()
Here you are attempting to create a WeatherManager without invoking the member wise initalizer, so Swift gives you the error message.
If you click on the error message itself you will see a Fix is offered, click that and Swift will change your code to:
var weatherManager = WeatherManager(delegate: <WeatherManagerDelegate?>)
Select the <WeatherManagerDelegate?> and type the value you wish to pass.
HTH