在Swift中创建货币转换器

我想用Swift做一个货币兑换器。我看到了这篇帖子：还有

所以当我把它们结合在一起时：

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()

它向我返回如下输出：

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

---

但我想访问货币汇率。我该怎么做？我不知道该怎么做？

返回的数据是一个字符串，其中的值用逗号分隔，因此我的方法是：

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

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

let exchangeRate = values[1].doubleValue

---

返回的数据是一个字符串，其中的值用逗号分隔，因此我的方法是：

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

let exchangeRate = values[1].doubleValue

Swift 3版本： 我很难在Swift 3中编译被接受的答案。以下是我在swift 3中的工作：

    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()

Swift 3版本： 我很难在Swift 3中编译被接受的答案。以下是我在swift 3中的工作：

    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()

---

我在Swift 5中制作了一个更简单的货币转换器。如果您感兴趣，请访问我的GitHub：

用法非常简单：

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!) •••")
    })
}

}

如果您想了解如何制作，可以在此处学习Swift代码：

---

它基本上是一个XML解析器，从以下来源获取数据：

我在Swift 5中制作了一个更简单的货币转换器。如果您感兴趣，请访问我的GitHub：

用法非常简单：

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!) •••")
    })
}

}

如果您想了解如何制作，可以在此处学习Swift代码：

---

它基本上是一个从以下来源获取数据的XML解析器：

这真是一个优雅且轻量级的解析器。非常感谢这真的很优雅，很轻。非常感谢你