adilanchian · February 22, 2018 00:05 · Feb 22, 2018
diff --git a/FriendProtocol.swift b/FriendProtocol.swift
@@ -0,0 +1,60 @@
+import UIKit
+
+/*
+  Protocol Definition: A protocol defines a blueprint of methods, properties, and other requirements that suit a particular 
+  task or piece of functionality.
+  (https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Protocols.html)
+*/
+
+/*
+  This protocol, GreetFriendDelegate, requires any conforming type to have an instance method called greetFriend, which 
+  returns a String value whenever it’s called
+*/
+protocol GreetFriendDelegate {
+    func greetFriend() -> String
+}
+
+/*
+  This is the initial view controller. I want to navigate to my FriendViewController and have Liam greet me!
+*/
+class MeViewController: UIViewController, GreetFriendDelegate {
+    let myName = "Alec"
+
+    // Im getting ready to navigate to my FriendViewController... //
+    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
+        if let destination = segue.destination as? FriendViewController {
+            print("Navigating to FriendViewController...")
+            destination.delegate = self
+            print("Set MeViewController as the delegate for FriendViewController.")
+        }
+    }
+
+    /*
+      You need to implement your function definition here to CONFORM to the protocol. When my friend Liam is ready, 
+      he will use a button to greet me! Liam needs to know my name, though. So I'll remind him by sending it to 
+      him when he asks for it.
+    */
+    func greetFriend() -> String {
+        print("I am a protocol method getting called from FriendViewController.")
+        return self.myName
+    }
+}
+
+/*
+  This is the secondary view controller that is reached by navigating from the MeViewController.
+*/
+class FriendViewController: UIViewController {
+    let myName = "Liam"
+    /* 
+      We set our delegate property here to have reference to the MeViewController so we can ask it for the name to greet 
+      when Liam needs it. 
+    */
+    var delegate: GreetFriendDelegate?
+
+    // Liam needs his friends name here! Hurry, ask MeViewController! //
+    @IBAction func greetFriendAction(_ sender: Any) {
+        // Liam is asking MeViewController who he should greet //
+        let myFriend = self.delegate?.greetFriend()
+        print("Hello, \(myFriend)! My name is \(self.myName)")
+    }
+}