Programming Fundamentals/Conditions/Swift

conditions.swift

// This program asks the user for a Fahrenheit temperature, 
// converts the given temperature to Celsius,
// and displays the results.
//
// References:
//     https://www.mathsisfun.com/temperature-conversion.html
//     https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html

func getChoice() -> String {
    var choice: String

    print("Enter C to convert to Celsius or F to convert to Fahrenheit:")
    choice = readLine(strippingNewline: true)!

    return choice
}

func getTemperature(label: String) -> Double {
    var temperature: Double
    
    print("Enter " + label + " temperature:")
    temperature = Double(readLine(strippingNewline: true)!)!
    
    return temperature
}

func calculateCelsius(fahrenheit: Double) -> Double {
    var celsius: Double
    
    celsius = (fahrenheit - 32) * 5 / 9
    
    return celsius
}

func calculateFahrenheit(celsius: Double) -> Double {
    var fahrenheit: Double
    
    fahrenheit = celsius * 9 / 5 + 32
    
    return fahrenheit
}

func displayResult(temperature: Double, fromLabel: String, result: Double, toLabel: String) {
    print(String(temperature) + "° " + fromLabel + " is " + String(result) + "° " +  toLabel)
}

func main() {
    // main could either be an if-else structure or a switch-case structure

    var choice: String
    var temperature: Double
    var result: Double

    choice = getChoice()

    // if-else approach    
    if choice == "C" || choice == "c" {
        temperature = getTemperature(label:"Fahrenheit")
        result = calculateCelsius(fahrenheit:temperature)
        displayResult(temperature:temperature, fromLabel:"Fahrenheit", result:result, toLabel:"Celsius")    } 
    else if choice == "F" || choice == "f" {
        temperature = getTemperature(label:"Celsius")
        result = calculateFahrenheit(celsius:temperature)
        displayResult(temperature:temperature, fromLabel:"Celsius", result:result, toLabel:"Fahrenheit")
    } 
    else {
        print("You must enter C to convert to Celsius or F to convert to Fahrenheit.")
    }

    // switch-case approach
    switch choice {
        case "C", "c":
            temperature = getTemperature(label:"Fahrenheit")
            result = calculateCelsius(fahrenheit:temperature)
            displayResult(temperature:temperature, fromLabel:"Fahrenheit", result:result, toLabel:"Celsius")
        case "F", "f":
            temperature = getTemperature(label:"Celsius")
            result = calculateFahrenheit(celsius:temperature)
            displayResult(temperature:temperature, fromLabel:"Celsius", result:result, toLabel:"Fahrenheit")
        default:
            print("You must enter C to convert to Celsius or F to convert to Fahrenheit.")
    }
}

main()
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Copy and paste the code above into one of the following free online development environments or use your own Swift compiler / interpreter / IDE.
conditions.swift

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See Also
