How can I reuse a variable later on in Swift - swift

Question

I'm trying to capture a user input (textfield + button) and reuse the result later in the program but I don't know how to do that.
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var resultLabel: UILabel!
#IBOutlet weak var moneyTextField: UITextField!
#IBAction func convert(_ sender: Any) {
let convertion:Double = Double(moneyTextField.text!)!
print(convertion)
}
override func viewDidLoad() {
super.viewDidLoad()
let url = URL(string: "https://www.x-rates.com/calculator/?from=EUR&to=USD&amount=1")!
let request = NSMutableURLRequest(url : url)
let task = URLSession.shared.dataTask(with: request as URLRequest) {
data, response, error in
var rateValue:Double = 0.0;
if let error = error {
print(error)
} else {
if let unwrappedData = data {
let dataString = NSString(data: unwrappedData, encoding: String.Encoding.utf8.rawValue)
var stringSeperator = "<span class=\"ccOutputRslt\">"
if let contentArray = dataString?.components(separatedBy: stringSeperator){
if contentArray.count > 0 {
stringSeperator = "<span"
let newContentArray = contentArray[1].components(separatedBy: stringSeperator)
if newContentArray.count > 0 {
rateValue = Double(newContentArray[0])!
print(newContentArray[0])
}
}
}
}
}
//
print("Rate is \(rateValue)");
DispatchQueue.main.sync(execute: {
self.resultLabel.text = "the value of the dollar is " + String(rateValue)
}
)}
task.resume()
}
}
What I want to do is take the let convertion and multiply it by rateValue at the end of the code. I tried different thing but without any results.
after the advice from Joakim Danielson
I did that :
import UIKit
class ViewController: UIViewController {
var fxRate: Double?
#IBOutlet weak var resultLabel: UILabel!
#IBOutlet weak var moneyTextField: UITextField!
#IBAction func convert(_ sender: Any) {
let convertion:Double = Double(moneyTextField.text!)!
print(convertion)
var convertedAmount = 0.0
if let rate = fxRate, let money = Double(moneyTextField.text) {
convertedAmount = rate * money
}
print(convertedAmount)
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
let url = URL(string: "https://www.x-rates.com/calculator/?from=EUR&to=USD&amount=1")!
let request = NSMutableURLRequest(url : url)
let task = URLSession.shared.dataTask(with: request as URLRequest) {
data, response, error in
var rateValue:Double = 0.0;
if let error = error {
print(error)
} else {
if let unwrappedData = data {
let dataString = NSString(data: unwrappedData, encoding: String.Encoding.utf8.rawValue)
var stringSeperator = "<span class=\"ccOutputRslt\">"
if let contentArray = dataString?.components(separatedBy: stringSeperator){
if contentArray.count > 0 {
stringSeperator = "<span"
let newContentArray = contentArray[1].components(separatedBy: stringSeperator)
if newContentArray.count > 0 {
rateValue = Double(newContentArray[0])!
print(newContentArray[0])
rateValue = Double(newContentArray[0])!
self.fxRate = rateValue
}
}
}
}
}
//
print("Rate is \(rateValue)");
DispatchQueue.main.sync(execute: {
self.resultLabel.text = "the value of the dollar is " + String(rateValue)
}
)}
task.resume()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
but I have the error : Cannot invoke initializer for type 'Double' with an argument list of type '(String?)' on line 26. Can you please help me? thx!

Answer 1

create a variable outside of your function
var anyVariableYouWantToAccessLater: Double?
And use this variable anywhere you want.

Answer 2

Since you're downloading the rate during viewDidLoad I am assuming this is what you want to keep.
Add a new property to the class
class ViewController: UIViewController {
var fxRate: Double?
...
In viewDidLoad update this property with the downloaded value
rateValue = Double(newContentArray[0])!
fxRate = rateValue
In the convert func (or wherever you want to use the rate)
#IBAction func convert(_ sender: Any) {
var convertedAmount = 0.0
if let rate = fxRate, let money = Double(moneyTextField.text ?? "0") {
convertedAmount = rate * money
}
print(convertedAmount)
}