how to use range slider with Dates instead of numbers in Swift?

Question

I am looking at this implementation of range slider: https://github.com/warchimede/RangeSlider and I see that it has a lowerValue and upperValue set by default to 0.2 and 0.8:

@IBInspectable var lowerValue: Double = 0.2 {
    didSet {
        if lowerValue < minimumValue {
            lowerValue = minimumValue
        }
        updateLayerFrames()
    }
}

@IBInspectable var upperValue: Double = 0.8 {
    didSet {
        if upperValue > maximumValue {
            upperValue = maximumValue
        }
        updateLayerFrames()
    }
}

It also has minimumValue and maximumValue set to 0 and 1:

@IBInspectable var minimumValue: Double = 0.0 {
    willSet(newValue) {
        assert(newValue < maximumValue, "RangeSlider: minimumValue should be lower than maximumValue")
    }
    didSet {
        updateLayerFrames()
    }
}

@IBInspectable var maximumValue: Double = 1.0 {
    willSet(newValue) {
        assert(newValue > minimumValue, "RangeSlider: maximumValue should be greater than minimumValue")
    }
    didSet {
        updateLayerFrames()
    }
}

I would like to change the behavior of this slider so that it becomes range date picker - the maximumValue should be the current date and minimumValue some date in the past, e.g. 6 months before. Could you help me with that and give some hints whether it's possible to do so with this range slider?

Answer 1

This should do it.

class ViewController: UIViewController {

    var slider:UISlider?
    // These number values represent each slider position
    let daysInPast = [14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0] //Add your values here - this sets from two past weeks to current day
    let secondsPerDay = 86400
    var oldIndex = 0

    override func viewDidLoad() {
        super.viewDidLoad()
        slider = UISlider(frame: self.view.bounds)
        self.view.addSubview(slider!)

        // slider values go from 0 to the number of values in your numbers array
        var numberOfSteps = Float(numbers.count - 1)
        slider!.maximumValue = numberOfSteps;
        slider!.minimumValue = 0;

        // As the slider moves it will continously call the -valueChanged:
        slider!.continuous = true; // false makes it call only once you let go
        slider!.addTarget(self, action: "valueChanged:", forControlEvents: .ValueChanged)
    }

    func valueChanged(sender: UISlider) {
        // round the slider position to the nearest index of the numbers array
        var index = (Int)(slider!.value + 0.5);
        slider?.setValue(Float(index), animated: false)
        var dayInPast = daysInPast[index]; // <-- This numeric value you want

        if oldIndex != index {

            let today = NSDate() //today
            //every day value in the slider will be multiplied by number of seconds in day
            let pickedDate = today.dateByAddingTimeInterval(-secondsPerDay * dayInPast)
            let calendar = NSCalendar.currentCalendar()
            let components = calendar.components([.Month, .Year, .Day], fromDate: pickedDate)
            let month = components.month
            let year = components.year
            let day = components.day

            print("Date picked with slider is \(month)/\(day), \(year)")

            oldIndex = index
        }
    }
}