How can I write a simple example on how to use delegates in Swift 5 - ios

Question

I want to write a simple example on how delegates work in Swift. I've set up a class, a protocol and another class which adheres to the protocol. However I'm getting on two different places the same error. I've created a simple swift command line tool in xcode and all my code is inside main.swift. The code has no real functionality except learning how delegates work.
Here are the error messages:
Consecutive declarations on a line must be separated by ';'
Insert ';'
Expected '(' in argument list of function declaration
Expected '{' in body of function declaration
Expected 'func' keyword in instance method declaration
Insert 'func '
Expected declaration
Invalid redeclaration of 'delegate()' //or anything() in the other error
Here is the code:
class MainClass {
var delegate: MyProtocol? = nil
delegate.doAnything() //getting 1st error here
}
protocol MyProtocol {
func doAnything()
}
class OtherClass: MyProtocol {
let anything = MainClass()
anything?.delegate = self //getting 2nd error here
func doAnything() {
print("text")
}
}

Answer 1

So the first error is because you are trying to call the delegate function, outside of anywhere it can be executed. You need to create a function that calls that function, or call it in init. When making examples, try using real world concepts to model your example. You could do something like a Conductor class and a Train Class. The conductor could implement some control protocol that controls the speed of the train.
Anyway, your second error is because self has not yet been initialized. to assign a variable to self, you must initialize the class first, so you could do
init() {
anything?.delegate = self
}
Feel free to DM to understand this concept more, i'll post a full example here in a bit.
EDIT: FULL EXAMPLE, feel free to ask questions
import Foundation
enum Direction {
case north
case east
case south
case west
}
protocol VehicleControls {
var speed: Float {get set}
var direction: Direction {get set}
var numPassengers: Int {get}
func change(newSpeed: Float)
func change(newDirection: Direction)
func createNoise()
}
class Conductor {
var vehicle: VehicleControls
init() {
vehicle = Train(s: 1.5, d: .west, nP: 50)
}
func controlVehicle() {
vehicle.change(newSpeed: 2.5)
vehicle.change(newDirection: .east)
vehicle.createNoise()
print("\n")
}
}
class Train: VehicleControls {
var speed: Float
var direction: Direction
var numPassengers: Int
init() {
self.speed = 0
self.direction = .north
self.numPassengers = 0
}
init(s: Float, d: Direction, nP: Int) {
self.speed = s
self.direction = d
self.numPassengers = nP
}
func change(newSpeed: Float) {
print("changing speed from \(speed), to \(newSpeed)")
self.speed = newSpeed
}
func change(newDirection: Direction) {
print("changing direction from \(direction) to \(newDirection)")
self.direction = newDirection
}
func createNoise() {
print("Chugga, Chugga... Chugga, Chugga... CHOO CHOO")
}
}
class Car: VehicleControls {
var speed: Float
var direction: Direction
var numPassengers: Int
init() {
self.speed = 0
self.direction = .north
self.numPassengers = 0
}
init(s: Float, d: Direction, nP: Int) {
self.speed = s
self.direction = d
self.numPassengers = nP
}
func change(newSpeed: Float) {
print("changing speed from \(speed), to \(newSpeed)")
self.speed = newSpeed
}
func change(newDirection: Direction) {
print("changing direction from \(direction) to \(newDirection)")
self.direction = newDirection
}
func createNoise() {
print("HONK HONK, BEEP BEEP")
}
}
let newConductor = Conductor()
newConductor.controlVehicle()
newConductor.vehicle = Car(s: 60.56, d: .north, nP: 2)
newConductor.controlVehicle()

Answer 2

edit your code in playground file:
protocol MyProtocol {
func doAnything()
}
class MainClass {
var delegate: MyProtocol? = nil
func callMeForGetCallBackWithDelegate() {
// send call back inside any function after call or inside in init
if let delegate = self.delegate {
delegate.doAnything()
}
}
}
class OtherClass: MyProtocol {
let anything = MainClass()
init() {
self.anything.delegate = self // set delegate in init or set inside any function
self.anything.callMeForGetCallBackWithDelegate()
}
func doAnything() {
print("text")
}
}
let otherClass = OtherClass()