How can I go about controlling 1 view controller from another? - ios

Question

So I have the following layout for my iOS app.
What I'm intending to do is put a table view in the purpleVC to control the Green viewcontroller...the top peachVC will have text in it which will need to change. I'm just not sure how to control one view controller from another. This includes having the purple slide in and out when a button on the GreenVC is clicked. I know there are classes out there to do this however I want to learn as well.
TESTING DELEGATES:
MAINVIEW CONTROLER
import UIKit
protocol Purpleprotocol {
func buttonpressed()
}
protocol Greenprotocol {
}
extension UIViewController {
func alert(message: String, title: String = "") {
let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
let OKAction = UIAlertAction(title: "OK", style: .default, handler: nil)
alertController.addAction(OKAction)
self.present(alertController, animated: true, completion: nil)
}
}
class MainViewController: UIViewController,Purpleprotocol,Greenprotocol {
weak var infoNav : UINavigationController?
weak var greenVC: GreenVC?
weak var purpleVC: PurpleVC?
weak var peachVC: PeachVC?
func buttonpressed() {
alert(message: "This is message")
print("buttonpressed")
let date = Date()
let calendar = Calendar.current
let hour = calendar.component(.hour, from: date)
let minutes = calendar.component(.minute, from: date)
greenVC?.greenlabel.text = String(hour) + ":" + String(minutes)
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "contentSegue" {
let infoNav = segue.destination as! UINavigationController
}
}
}
PURPLEVIEW CONTROLER
class PurpleVC: UIViewController {
var delegate: Purpleprotocol?
#IBAction func butclick(_ sender: UIButton) {
alert(message: "infunction")
delegate?.buttonpressed()
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
Thanks
R

Answer 1

It does depend on the case but to see a few examples:
A) You can connect it through the delegates. Your main view controller has 3 child view controllers to which it should report changes. It should also assign itself as a delegate to all 3 child controllers where it will get all notifications for events. This would look like
func purpleViewController(sender: PVC, selectedItem: Item) {
self.greenViewController.showItem(item: selectedItem)
self.peachVC.showItem(item: selectedItem)
}
func purpleViewController(sender: PVC, shouldSetMenuClosed closed: Bool) {
self.menuConstraint.constant = closed ? targetWidth : 0.0
}
B) You may have a data model which controls the whole screen and has a delegate for each of the children. The model will report any changes to its delegates so they may react accordingly. Main view controller would create an instance of this model when it loads and pass it to all of the children view controllers. The children would then directly manipulate the model:
In green controller:
func onTap() {
mode.menuShown = !mode.menuShown
}
In model:
var menuShown: Bool = true {
didSet {
self.menuDelegate.model(self, changedMenuShownStateTo: menuShown)
}
}
In main view controller:
func model(_ sender: Model, changedMenuShownStateTo shown:Bool) {
self.menuConstraint.constant = shown ? 0.0 : targetWidth
}
C) You can use notifications where any of the controllers may post to notification center a custom notification and other controllers may observe the notifications and act accordingly.
There are many other ways in doing so but these probably most popular. See if any of them fits you...

Answer 2

Delegation.
Your MainViewController will become a delegate to each of the embedded VC's that want to pass back information. From your description you'll need two delegate relationships:
protocol PurpleProtocol {
func selected(row: Int, text: String)
}
protocol GreenProtocol {
func slideButtonPressed()
}
Have MainViewController implement these protocols. Give identifiers to the embed segues. You can find them in the Document Outline view. In prepareForSegue, retain pointers to the embedded VC's and pass your self as the delegate:
class MainViewController: UIViewController, PurpleProtocol, GreenProtocol {
weak var greenVC: GreenViewController?
weak var purpleVC: PurpleViewController?
weak var peachVC: PeachViewController?
func selectedRow(row: Int, text: String) {
// do something useful
}
func slideButtonPressed() {
// slide purple view in or out depending on current state
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "EmbedPurple" {
let dvc = segue.destination as! PurpleViewController
purpleVC = dvc
dvc.delegate = self
}
else if segue.identifier = "EmbedGreen" {
let nav = segue.destination as! UINavigationController
let dvc = nav.topViewController as! GreenViewController
greenVC = dvc
dvc.delegate = self
} else if segue.identifier = "EmbedPeach" {
peachVC = segue.destination as! PeachViewController
}
}
}
In your embedded VC's, add a delegate pointer and call the delegate with the protocol method when it is time:
class GreenViewController: UIViewController {
weak var delegate: GreenProtocol?
#IBAction slideButtonPressed(sender: UIButton) {
delegate?.slideButtonPressed()
}
}
class PurpleViewController: UITableViewController {
weak var delegate: PurpleProtocol?
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
delegate?.selected(row: indexPath.row, text: modelArray[indexPath.row])
}
}