Creating a currency converter in Swift

Question

I am trying to make a currency converter in Swift. I saw this post: Need API for currency converting and How to make an HTTP request in Swift?.

So when I combined them together:

let url = NSURL(string: "http://download.finance.yahoo.com/d/quotes.csv?s=USDEUR=X&f=nl1d1t1");

let task = NSURLSession.sharedSession().dataTaskWithURL(url!) {(data, response, error) in
     println(NSString(data: data, encoding: NSUTF8StringEncoding))
}

task.resume()

It returns me a output as such:

Optional("USD to EUR",0.7987,"11/20/2014","3:45am")

But I want to access the currency exchange rate. How do I do that? I am not sure how to do that?

score 6 · Answer 1 · answered May 27 '19 at 20:15

I've made a simpler currency converter in Swift 5. If you're interested, check it out in my GitHub: https://github.com/ThiagoAM/CurrencyConverter

The usage is really simple:

class ViewController: UIViewController {

// Creates the Currency Converter instance:
let currencyConverter = CurrencyConverter()

override func viewDidLoad() {
    super.viewDidLoad()

    // Updates the exchange rates:
    currencyConverter.updateExchangeRates(completion: {
        // The code inside here runs after all the data is fetched.

        // Now you can convert any currency:
        // • Example_1 (USD to EUR):
        let doubleResult = self.currencyConverter.convert(10, valueCurrency: .USD, outputCurrency: .EUR)
        print("••• 10 USD = \(doubleResult!) EUR •••")

        // • Example_2 (EUR to GBP) - Returning a formatted String:
        let formattedResult = self.currencyConverter.convertAndFormat(10, valueCurrency: .EUR, outputCurrency: .GBP, numberStyle: .decimal, decimalPlaces: 4)
        print("••• Formatted Result (10 EUR to GBP): \(formattedResult!) •••")
    })
}

}

If you want to learn how to make it, you can study the Swift code here: https://github.com/ThiagoAM/CurrencyConverter/blob/master/CurrencyConverter.swift
It's basically a XML parser that fetches the data from the following source: https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml

score 2 · Accepted Answer · answered Nov 21 '14 at 13:10

2

if let string = NSString(data: data, encoding: NSUTF8StringEncoding) {
    let exchangeRate = string.componentsSeparatedByString(",")[1].doubleValue
}

answered Nov 21 '14 at 13:10

Ivica M.

4,763
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score 1 · Answer 3 · answered Nov 21 '14 at 13:11

The data returned is a string where the values are separated by commas, so this would be my approach:

var dataString = NSString(data: data, encoding: NSUTF8StringEncoding)
let values = dataString.componentsSeparatedByString(",")

let exchangeRate = values[1].doubleValue

score 1 · Answer 4 · answered Oct 11 '17 at 02:02

Swift 3 version: I had trouble getting the accepted answers to compile in Swift 3. Here is what I was able to get to work in swift 3:

    guard let url = URL(string: "https://download.finance.yahoo.com/d/quotes.csv?s=USDEUR=X&f=nl1d1t1") else {
        print("Error: cannot create translation URL")
        return
    }

    let loadRequest = URLRequest(url:url)

    URLSession.shared.dataTask(with: loadRequest, completionHandler: { (data, response, error) in
        if let error = error {
            #if DEBUG
                print("Error: data task error for translation \(error)")
            #endif
            return
        }

        guard let data = data else {
            #if DEBUG
                print("Error: data null for translation")
            #endif
            return
        }
        if let translationString = String(data: data, encoding: String.Encoding(rawValue: String.Encoding.utf8.rawValue)) {
            #if DEBUG
                print(translationString)
            #endif

            let exchangeRateArray = translationString.components(separatedBy: ",")
            let exchangeRate: Double = Double(exchangeRateArray[1])!
            print(exchangeRate)
        }
        else {
            #if DEBUG
                print("Error generating string from data in translation")
            #endif
            return
        }

    }).resume()

Creating a currency converter in Swift

4 Answers4