selecting UISegmentedController segment outside of view controller

Question

I have a ViewController with layered container views in it, along with this SegmentedController code:

@IBOutlet weak var dayPicker: UISegmentedControl!

@IBAction func dayPickerControl(sender: UISegmentedControl) {

    switch dayPicker.selectedSegmentIndex {
    case 0:
        monContainer.hidden = false
        tuesContainer.hidden = true
        wedContainer.hidden = true
        thursContainer.hidden = true
        friContainer.hidden = true
        satContainer.hidden = true
        sunContainer.hidden = true
    case 1:
        monContainer.hidden = true
        tuesContainer.hidden = false
        wedContainer.hidden = true
        thursContainer.hidden = true
        friContainer.hidden = true
        satContainer.hidden = true
        sunContainer.hidden = true
    case 2:
        monContainer.hidden = true
        tuesContainer.hidden = true
        wedContainer.hidden = false
        thursContainer.hidden = true
        friContainer.hidden = true
        satContainer.hidden = true
        sunContainer.hidden = true
    case 3:
        monContainer.hidden = true
        tuesContainer.hidden = true
        wedContainer.hidden = true
        thursContainer.hidden = false
        friContainer.hidden = true
        satContainer.hidden = true
        sunContainer.hidden = true
    case 4:
        monContainer.hidden = true
        tuesContainer.hidden = true
        wedContainer.hidden = true
        thursContainer.hidden = true
        friContainer.hidden = false
        satContainer.hidden = true
        sunContainer.hidden = true
    case 5:
        monContainer.hidden = true
        tuesContainer.hidden = true
        wedContainer.hidden = true
        thursContainer.hidden = true
        friContainer.hidden = true
        satContainer.hidden = false
        sunContainer.hidden = true
    case 6:
        monContainer.hidden = true
        tuesContainer.hidden = true
        wedContainer.hidden = true
        thursContainer.hidden = true
        friContainer.hidden = true
        satContainer.hidden = true
        sunContainer.hidden = false
    default:
        break;
    }

How can I select a certain segment from another view controller so that when I return to this View the container that I want is visible and the corresponding segment is selected?

Answer 1

First you need to be saving global state somewhere for any part of your application to access. Even something as simple as a shared object (singleton) or an object tied to UIApplicationDelegate will do fine here.

One option is to use the singleton method. A lot of people don't like to use singletons for various reasons but I think it's an easy illustration of a global value in this case. The point of a singleton is to keep an object around for the lifetime of the application. An alternative would be to tie this state to UIApplicationDelegate .

To implement the singleton (you can put this in its own file if you wish, I called it UserState but you can change that to whatever you want):

private let _UserStateSharedInstance = UserState()

class UserState  {
    class var sharedInstance : UserState {
        return _UserStateSharedInstance
    }
    var selectedDay = 0
}

In this view controller you can retrieve the selected day:

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    dayPicker.selectedSegmentIndex = UserState.sharedInstance.selectedDay
}

@IBAction func dayPickerControl(sender: UISegmentedControl) {
    UserState.sharedInstance.selectedDay = sender.selectedSegmentIndex // You probably also want to set this here

    // Do your switching here
}

In your other view controller you can set your selected day:

@IBAction func dayPickerControl(sender: UISegmentedControl) {
    UserState.sharedInstance.selectedDay = sender.selectedSegmentIndex
}

---

While we're at it, might I suggest an easier way to do this switching?

We might start out by combining each case into a simple logical statement to avoid having to repeat the list over and over again:

@IBAction func dayPickerControl(sender: UISegmentedControl) {

    let segmentIndex = sender.selectedSegmentIndex

    monContainer.hidden = (segmentIndex != 0)
    tuesContainer.hidden = (segmentIndex != 1)
    wedContainer.hidden = (segmentIndex != 2)
    thursContainer.hidden = (segmentIndex != 3)
    friContainer.hidden = (segmentIndex != 4)
    satContainer.hidden = (segmentIndex != 5)
    sunContainer.hidden = (segmentIndex != 6)
}

Now it's becoming more obvious that this is just an array of views that we want to hide/show depending on an index. We might rewrite this with a loop:

var viewsToHide: [UIView]?

override func viewDidLoad() {
    super.viewDidLoad()

    viewsToHide = [monContainer, tuesContainer, wedContainer, thursContainer, friContainer, satContainer, sunContainer]
}

@IBAction func dayPickerControl(sender: UISegmentedControl) {

    let segmentIndex = sender.selectedSegmentIndex

    for (index, view) in enumerate(viewsToHide ?? []) {
        view.hidden = (segmentIndex != index)
    }
}