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Engineering LibreTexts

4.16: Swift Examples

  • Page ID
    10652
  • Temperature

    The temperature program main function is listed twice, once using if-then-else and once using switch, followed by the supporting functions.

    If Then Else

    // 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 main() {
        var choice: String
        
        choice = getChoice()
        if choice == "C" || choice == "c" {
            processCelsius()
        } 
        else if choice == "F" || choice == "f" {
            processFahrenheit()
        } 
        else {
            print("You must enter C to convert to Celsius or F to convert to Fahrenheit.")
        }
    }
    
    main()
    

    Switch

    func main() {
        var choice: String
        
        choice = getChoice()
        switch choice {
            case "C", "c":
                processCelsius()
            case "F", "f":
                processFahrenheit()
            default:
                print("You must enter C to convert to Celsius or F to convert to Fahrenheit.")
        }
    }
    

    Supporting Functions

    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 processCelsius() {
        var temperature: Double
        var result: Double
    
        temperature = getTemperature(scale:"Fahrenheit")
        result = calculateCelsius(fahrenheit:temperature)
        displayResult(temperature:temperature, fromScale:"Fahrenheit", result:result, toScale:"Celsius")
    }
    
    func processFahrenheit() {
        var temperature: Double
        var result: Double
    
        temperature = getTemperature(scale:"Celsius")
        result = calculateFahrenheit(celsius:temperature)
        displayResult(temperature:temperature, fromScale:"Celsius", result:result, toScale:"Fahrenheit")
    }
    
    func getTemperature(scale: String) -> Double {
        var temperature: Double
        
        print("Enter " + scale + " 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, fromScale: String, result: Double, toScale: String) {
        print(String(temperature) + "° " + fromScale + " is " + String(result) + "° " +  toScale)
    }
    

    Output

    Enter C to convert to Celsius or F to convert to Fahrenheit:
     c
    Enter Fahrenheit temperature:
     100
    100.0° Fahrenheit is 37.77777777777778° Celsius
    
    Enter C to convert to Celsius or F to convert to Fahrenheit:
     f
    Enter Celsius temperature:
     100
    100.0° Celsius is 212.0° Fahrenheit
    
    Enter C to convert to Celsius or F to convert to Fahrenheit:
     x
    You must enter C to convert to Celsius or F to convert to Fahrenheit.