Creating THREE pickerViews for converting the units

Question

Here is the main screen of the app :

I have successfully linked these pickerView to each other, then I have tried to assign the calculation in converting but not to avail :

ex: mile to killo but I could not find a way to do so. I have tried to use "Switch" still nothing happen. I just need someone can show me how can I convert from a certain unit to another unit through the textFields. For example, if you enter a value in a certain texField the converted result will in the other textField and vise versa.

Here is my Code:

    import UIKit

class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate, UITextFieldDelegate{

@IBOutlet weak var mainPicker: UIPickerView!
@IBOutlet weak var leftPicker: UIPickerView!
@IBOutlet weak var rightPicker: UIPickerView!
@IBOutlet weak var textFieldLeft: UITextField!
@IBOutlet weak var textFielfRight: UITextField!
@IBOutlet weak var equal: UILabel!


var leftPickerData : [String] = []
var rightPickerData : [String] = []

var dataDict:NSMutableDictionary!
var mainPickerData:NSArray!
var leftRightPickerData:NSArray!

//yourPicker.backgroundColor = UIColor(patternImage: UIImage(named: "back.jpg")!)


override func viewDidLoad() {
    super.viewDidLoad()

    mainPicker.backgroundColor = .clear
    rightPicker.backgroundColor = .clear
    leftPicker.backgroundColor = .clear

    // Connect data to ViewController ..
    self.mainPicker.delegate = self
    self.mainPicker.dataSource = self

    self.leftPicker.delegate = self
    self.leftPicker.dataSource = self

    self.rightPicker.delegate = self
    self.rightPicker.dataSource = self

    self.textFieldLeft.delegate = self
    self.textFielfRight.delegate = self

    let theWidth = view.frame.size.width
    let theHeight = view.frame.size.height

    mainPicker.center = CGPoint(x: theWidth/2, y: theHeight/2 - 182.5)
    leftPicker.center = CGPoint(x: theWidth/2 - 100, y: theHeight/2)
    rightPicker.center = CGPoint(x: theWidth/2 + 100, y: theHeight/2)
    textFieldLeft.center = CGPoint(x: theWidth/2 - 90, y: theHeight/2 + 110)
    textFielfRight.center = CGPoint(x: theWidth/2 + 90, y: theHeight/2 + 110)
    equal.center = CGPoint(x: theWidth/2, y: theHeight/2 + 110)



    dataDict = ["Area":["Square Mile", "Square Yard", "Square Foot", "Square Inch", "Hectare", "Acre", "Square Kilometer", "Square Meter", "Square Centimeter", " Square Millimeter"]
        ,"Energy":["Btus", "Calories", "Ergs", "Foot-Pounds", "Joules", "Kilogram-Calories", "Kilogram-Meters", "Kilowatt-Hours", "Newton-Meters", "Watt-Hours"], "Length":["Mile", "Yard", "Foot", "Inch", "Kilometer", "Meter", "Centimeter", "Millimeter"], "Power": ["Btus/Minute", "Foot-Pounds/Min", "Foot-Pounds/Sec", "Horsepower", "Kilowatts", "Watts"], "Pressure": ["Pounds/Sqr Ft", "Pounds/Sqr In", "Atmospheres", "Bars", "In of Mercury", "Cm of Mercury", "Kilograms/Sqr Meter", "Pascals"], "Speed": ["Knots", "Miles/Hr", "Miles/Min", "Feet/Min", "Feet/Sec", "Kilometers/Hr", "Kilometer/Min", "Meters/Sec"], "Temperature": ["Celsius C˚", "Fahrenheit", "Kelvin"], "Time": ["Years", "Months", "Weeks", "Days", "Hours", "Minutes", "Seconds", "Millisconds", "Microseconds", " Nanoseconds"], "Volume": ["Cupic Feet","Cubic Meter", "Gallon (Imp)", "Gallon (US)", "Quart (US)", "Pint (US)", "Fluid Oz", "Cup", "Tablespoon", "Teaspoon", "Dram (US)", "Liter"], "Weight": ["Short Ton (US)","Long Ton (UK)", "Pound (U.S)", "Ounce (US)", "Stone", "Metric Ton", "Kilogram", "Gram"]]
    mainPickerData = dataDict.allKeys as NSArray!;
    leftRightPickerData = dataDict.object(forKey: mainPickerData.firstObject as! String) as! NSArray

    // Linking the textFields with the pickerViews.
    //textFieldLeft.inputView = leftPicker;
   // textFielfRight.inputView = rightPicker;



    }



// The number of columns of data
func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return 1
}

// The number of rows of data
func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {

    switch (pickerView.tag) {

    case mainPicker.tag:

        return mainPickerData.count

    case leftPicker.tag,rightPicker.tag:

        let currentSelectedIndex = mainPicker.selectedRow(inComponent: component)
        leftRightPickerData = (dataDict.object(forKey: mainPickerData[currentSelectedIndex] as! String) as! NSArray)

        return leftRightPickerData.count;

    default:
        break;
    }
    return 0;
}

// The data to return for the row and component (column) that's being passed in
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {

    if leftPicker.tag == 2 {

        return leftPickerData[row]

    }else if rightPicker.tag == 3{

        return rightPickerData[row]

    }

    return ""
}

// Catpure the picker view selection
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    // This method is triggered whenever the user makes a change to the picker selection.
    // The parameter named row and component represents what was selected.

    if(pickerView.tag == 1 ){

        let currentSelectedIndex = mainPicker.selectedRow(inComponent: component)
        leftRightPickerData = (dataDict.object(forKey: mainPickerData[currentSelectedIndex] as! String) as! NSArray)

        leftPicker.reloadAllComponents()
        rightPicker.reloadAllComponents()

        if mainPicker.tag == mainPicker.selectedRow(inComponent: component) {

            if leftPicker.tag == leftPicker.selectedRow(inComponent: component) && rightPicker.tag == rightPicker.selectedRow(inComponent: component){

                textFieldLeft.text = textFielfRight.text
            }
        }

    }



}

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    self.view.endEditing(true)

}

func textFieldShouldReturn(_ textField: UITextField) -> Bool {

    textFieldLeft.resignFirstResponder()
    textFielfRight.resignFirstResponder()

    return true

}

func pickerView(_ pickerView: UIPickerView, attributedTitleForRow row: Int, forComponent component: Int) -> NSAttributedString? {

    let titleData : String?
    if(pickerView.tag == mainPicker.tag){
        titleData = mainPickerData[row] as? String;

    }
    else{

        let currentSelectedIndex = mainPicker.selectedRow(inComponent: 0)
        leftRightPickerData = (dataDict.object(forKey: mainPickerData[currentSelectedIndex] as! String) as! NSArray)

        titleData = leftRightPickerData[row] as? String;
    }

    let myTitle = NSAttributedString(string: titleData!, attributes: [NSFontAttributeName:UIFont(name: "Georgia", size: 12.0)!,NSForegroundColorAttributeName:UIColor.blue])
    return myTitle;

}

}

Answer 1

I will give you some tips:

1. Value in a text field is a String, you should convert it to Double and then multiply by different value between 2 units.
2. To save these different values, I have an idea: save [1, 1760, 5280, 63360, 1.609344, 1609.344, 160934.4, 1609344] for ["Mile", "Yard", "Foot", "Inch", "Kilometer", "Meter", "Centimeter", "Millimeter"] then do some math caculating.
3. You should listen to the notification UITextFieldTextDidChange for each UITextField to instantly calculate the equal value.

If you are a lazy developer, I found this for you: https://github.com/michalkonturek/MKUnits

Hope this helps.

Answer 2

I would do something like this as an example for different length values:

You would want to store some sort of array that tracks conversion values for each different unit of measurement, the best universal length unit is meters. It would be a good idea to make sure the corresponding value for each unit stays static, so create an enum:

enum Length: Int {
    case mile           = 0
    case yard           = 1
    case foot           = 2
    case inch           = 3
    case kilometer      = 4
    // ... keep going with all lenght units of measurement
}

Then you should make your array of values for conversions, this is an array of double's based on the length values I listed in the enum above for conversion to meters:

// Store values with corresponding indicies in array to the Length enum's values
let meterConversions:[Double] = [1609.34, 0.9144, 0.3048, 0.0254, 1,000]

// Store values of length unit descriptions to print after conversion in TextField, long hand or short hand whatever you prefer. (this is optional)
let lengthUnits = ["Mile", "Yard", "Foot", "Inch", "Kilometer"]

Then create some conversion methods:

// Convert length type to meters
func convertToMeters(type: Length, unitValue: Double) -> Double {
    return (meterConversions[type.rawValue] * unitValue)
}

// Convert meters back to length type
func convertFromMeters(type: Length, meterValue: Double) -> Double {
    return meterValue/meterConversions[type.rawValue]
}

// Convert from length type to other length type
func convertType(from: Length, to: Length, unitValue: Double) -> Double {

    // Convert from value to meters to start
    let fromValueToMeters:Double = convertToMeters(type: from, unitValue: unitValue)

    // Now use that value to convert back to desired unit
    let newUnitValue:Double = convertFromMeters(type: to, meterValue: fromValueToMeters)

    return newUnitValue
}

Then whenever the user selects a new row in either the left or right UIPickerView, update the calculation and handle it however you wish:

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {

    // Make sure there is actually some text in the left text field, otherwise return
    guard let text = textFieldLeft.text else { print("textFieldLeft doesn't contain any text"); return }

    // You are going to need a numerical (Double) value from the user's text
    let stringAsDouble = Double(text)

    // Now check that the text was actually a numerical value able to be converted to a double
    if let value = stringAsDouble {

        var typeA:Length!
        var typeB:Length!

        if pickerView == leftPicker {
            typeA = Length(rawValue: row)!
            typeB = Length(rawValue: rightPicker.selectedRow(inComponent: 0))!
            converted = convertType(from: typeA, to: typeB, unitValue: value)
        }
        else if pickerView == rightPicker {
            typeA = Length(rawValue: leftPicker.selectedRow(inComponent: 0))!
            typeB = Length(rawValue: row)!
            let value:Double = 0 // Determine user entered value from textField
            converted = convertType(from: typeA, to: typeB, unitValue: value)
        }

        updateValueAfterConversion(originalValue: value, originalType: typeA, convertedValue: converted, convertedType: typeB)
    } else {
        print("Couldn't convert text to double value")
    }
}

func updateValueAfterConversion(originalValue: Double, originalType: Length, convertedValue: Double, convertedType: Length) {
    // Update text in both fields, lengthUnits part is optional if you want to print unit along with value.
    // Update text on left side
    textFieldLeft.text = "\(originalValue) \(lengthUnits[originalType.rawValue])"
    // Update text on right side
    textFieldRight.text = "\(convertedValue) \(lengthUnits[convertedType.rawValue])"
}