错误：可选（Alamofire.AFError.invalidURL（“”））

Question

I am just starting to code with Swift, and I came across this error while building an app using Alamofire

The error is :

Error: Optional(Alamofire.AFError.invalidURL(""))

This is my code. Can someone help??

import UIKit
import Alamofire
import SwiftyJSON


class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {


    let baseURL = "https://apiv2.bitcoinaverage.com/indices/global/ticker/BTC"

    let currencyArray = ["AUD", "BRL","CAD","CNY","EUR","GBP","HKD","IDR","ILS","INR","JPY","MXN","NOK","NZD","PLN","RON","RUB","SEK","SGD","USD","ZAR"]

    let currencySymbolsArray = ["$", "R$", "$", "¥", "€", "£", "$", "Rp", "₪", "₹", "¥", "$", "kr", "$", "zł", "lei", "₽", "kr", "$", "$", "R"]

    var currencySymbol = ""

    var finalURL = ""


    //Pre-setup IBOutlets
    @IBOutlet weak var bitcoinPriceLabel: UILabel!
    @IBOutlet weak var currencyPicker: UIPickerView!

    // determine number of columns
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    // determine number of rows
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return currencyArray.count
    }

    // fill in each row with title from array
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return currencyArray[row]
    }

    // Print something when you select a row
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        print (currencyArray[row])

        finalURL = baseURL + currencyArray[row]
        print(finalURL)
        currencySymbol = currencyArray[row]
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        currencyPicker.delegate = self
        currencyPicker.dataSource = self

        getCurrencyData(url: finalURL)
    }


    //TODO: Place your 3 UIPickerView delegate methods here

//    //MARK: - Networking
//    /***************************************************************/
    func getCurrencyData(url: String) {
        Alamofire.request(url, method: .get)
            .responseJSON { response in
                if response.result.isSuccess {
                    print("Success! Got the currency data ")

                    let currencyJSON : JSON = JSON(response.result.value!)

                    self.updateCurrencyData(json: currencyJSON)
                } else {
                    print("Error: \(String(describing: response.result.error))")
                    self.bitcoinPriceLabel.text = "Connection issues"
                } 
            }
    }


//    //MARK: - JSON Parsing
//    /***************************************************************/

    func updateCurrencyData(json : JSON) {
        if let currencyResult = json["ask"].double  {
            bitcoinPriceLabel.text = " \(currencySymbol) +  \(currencyResult) "
        } else {
            bitcoinPriceLabel.text = "Currency unavailable"
        }
    }
}

Answer 1

The issue is that you are calling getCurrencyData from your view controllers viewDidLoad method, while the value of finalURL is still its initial value, namely "" , which is exactly what you see as the invalid URL in the error message.

You only need to make the network call once the user actually makes a selection using the picker.

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    currencySymbol = currencySymbolsArray[row]
    getCurrencyData(url: baseURL + currencyArray[row])
}

There's also no need for the finalURL variable, since you can directly input the data you stored in finalURL to the getCurrencyData function.

Unrelated to the error, but you were also setting wrong data to currencySymbol , since you were assigning data to it from the currencyArray rather than the currencySymbolArray .