Set up Delegate relationship between two views and send messages - ios

Question

In iOS, I am building an app in Swift. I have a View with a container view set up within it, linking an embedded view. This has been set up using Storyboards.
How do I set up a delegate relationship between the views in Swift code so that I can send messages / trigger functions in one view from the other?
Any help would be appreciated!

Answer 1

Suppose you have two views ViewA and ViewB
Instance of ViewB is created inside ViewA, so ViewA can send message to ViewB's instance, but for the reverse to happen we need to implement delegation (so that using delegate ViewB's instance could send message to ViewA)
Follow these steps to implement the delegation
1) In ViewB create protocol as
protocol ViewBDelegate{
func delegateMethod(controller:ViewB, text:String)
}
2) Declare the delegate in the sender class
class ViewB: UIView {
var delegate: ViewBDelegate! = nil
}
3) Use the method in class to call the delegate method as
#IBAction func callDelegateMethod(sender : UIBarButtonItem) {
delegate!. delegateMethod(self, text: colorLabel.text)
//assuming the delegate is assigned otherwise error
}
4) Adopt the protocol in ClassA
class ViewA: UIView, ViewBDelegate {
5) Implement the delegate
func delegateMethod(controller: ViewB, text: String) {
label.text = "The text is " + text
}
6) Set the delegate
override func anyFuction()
{
// create ViewB instance and set the delegate
viewB.delegate = self
}
Note : This is just the rough idea of delegation in swift between two classes, you can customize it as per your requirements.

Answer 2

Create a unique identifier for your embed segue.
In the parent view controller, implement the prepareForSegue method.
Use a switch statement to match the segue identifier. In the case for your contained view controller, fetch the destination view controller property from the segue, cast it to the type for your custom destination view controller, and set it's delegate property.
If you need a way to send parent-to-child messages on a continuing basis, you should also save a pointer to your child view controller in prepareForSegue.
(You will also need to define a protocol to communicate from the child to the parent, and set up the parent to conform to that protocol. You should use a name other than "delegate" for the delegate property. Say you call it `ParentVCDelegate" (Since lots of Apple's classes like UITableViewController already have a delegate property.)

Answer 3

I think you actually want to use a segue here? In a previous project I made an overloaded UIView controller that would pass data from controller to controller.
We had a data container class called RestFlightVariables and another container called rest which both stored specific information to be passed between controllers.
Then we created RESTUIViewController which had an overloaded prepareForSegue function. If the class the controller was segueing to was also a RESTUIViewController the variables rest and restVars would be passed on.
/**
RESTUIViewController is an overloaded UIVIewcontroller that handles the passing of REST variables between view controllers
*/
class RESTUIViewController : ResponsiveTextFieldViewController {
var rest : RESTInterface?
var restVars : RESTFlightVariables?
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
print("----- RESTUIViewController Segue -----")
let nextVC = segue.destinationViewController as RESTUIViewController
nextVC.rest = self.rest
nextVC.restVars = self.restVars
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
Another alternative could be to use the NSNotification System, but this isn't really appropriate when you are passing data between views. Segues is a more appropriate method of data passing.