Question about delegate and protocol in swift (with example) - ios

Question

I am trying to work with delegate and protocol but met a problem.
I created 2 buttons on one ViewController and created 1 imageView in another ShowViewController. The color of the imageView will change according to which button is pressed.
ViewController.swift
import UIKit
protocol getColorProtocol {
func getColor(color:String?)
}
class ViewController: UIViewController {
var color: String?
var delegate:getColorProtocol?
#IBAction func blueButtonPressed(_ sender: Any) {
color = "blue"
delegate?.getColor(color: color)
}
#IBAction func redButtonPressed(_ sender: Any) {
color = "red"
delegate?.getColor(color: color)
}
override func viewDidLoad() {
super.viewDidLoad()
}
}
ShowViewController.swift
import UIKit
class ShowViewController: UIViewController, getColorProtocol {
var viewOne = ViewController()
#IBOutlet weak var colorView: UIImageView!
func getColor(color: String?) {
print("color is \(color!)")
if color == "red"{
colorView.backgroundColor = UIColor(displayP3Red: 255/255, green: 0/255, blue: 0/255, alpha: 1)
}
else if color == "blue" {
colorView.backgroundColor = UIColor(displayP3Red: 0/255, green: 0/255, blue: 255/255, alpha: 1)
}
}
override func viewDidLoad() {
super.viewDidLoad()
viewOne.delegate = self
}
}
press here to view the storyboard!
You may check my storyboard above.
Currently, it has no error but it cannot call the getColor function. I am wondering if the problem is coming from the delegate?.getColor(color: color) statement.
Any ideas?

Answer 1

First of all, in your case, you don't need to use delegate pattern
Your ViewController connect directly to ShowViewController through segue
You can use prepareForSegue instead
Secondly, I don't think you understand how delegate pattern works,
Inside ShowViewController, you're create a new ViewController called viewOne, it isn't the original ViewController so that's why your code doesn't work as expected
As I mentioned above, you should use segue
first, go to the storyboard setup your segue identifier. Then, inside your ViewController
override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
if (segue.identifier == "goToShowVC") {
//your code here
}
}

Answer 2

You don't need a delegate for this, but just prepare for segue. I see that you have two segues set up already, so in your viewcontroller, assuming your segues are called "blue" and "red" in your storyboard, you could add:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destinationVC = segue.destination as? ShowViewController {
if segue.identifier == "blue" {
destinationVC.color = UIColor.blue
} else if segue.identifier == “red” {
destinationVC.color = UIColor.red
}
}
}
then you would want to add a color variable to manipulate in your showviewcontroller. For example:
var color = UIColor.white
colorview.backgroundcolor = color