Implementing delegation in Swift
You will want a delegate protocol, a delegator who truly delegates out the duties and a delegate object that implements the delegate protocol and does the precise work that was requested by the “boss”. Let’s translate this into human.
The consumer experiences a bug. The mission supervisor creates a problem and tells one of many builders to repair the issue asap.
See? That is delegation. Sooner or later an occasion occurred, so the delegator (supervisor) utilized an exterior useful resource (a developer) utilizing a standard interface (subject describing the issue for each get together) to do obtain one thing (repair the 🐛).
To exhibit how delegation works in actual life I made a reasonably easy instance. I will use an analogous method (as a result of Xcode playgrounds are nonetheless freezing each 1-5 minutes) like I did for the command sample, however the function of this one goes to be virtually completely completely different, as a result of we’re speaking about delegation. 😅
#!/usr/bin/env swift
import Basis
protocol InputDelegate {
var shouldContinueListening: Bool { get }
func didStartListening()
func didReceive(enter: String)
}
class InputHandler {
var delegate: InputDelegate?
func hear() {
self.delegate?.didStartListening()
repeat {
guard let enter = readLine() else {
proceed
}
self.delegate?.didReceive(enter: enter)
}
whereas self.delegate?.shouldContinueListening ?? false
}
}
struct InputReceiver: InputDelegate {
var shouldContinueListening: Bool {
return true
}
func didStartListening() {
print("👻 Please be good and say "hello", if you wish to go away simply inform me "bye":")
}
func didReceive(enter: String) {
change enter {
case "hello":
print("🌎 Whats up world!")
case "bye":
print("👋 Bye!")
exit(0)
default:
print("🔍 Command not discovered! Please attempt once more:")
}
}
}
let inputHandler = InputHandler()
let inputReceiver = InputReceiver()
inputHandler.delegate = inputReceiver
inputHandler.hear()That is how one can create your personal delegate sample in Swift. You possibly can think about that Apple is doing the identical factor beneath the hood, with UICollectionViewDataSource, UICollectionViewDelegate and so on. You solely should implement the delegate, they will present the protocol and the delegator. 🤔
Weak properties, delegates and courses
Reminiscence administration is a vital factor so it is price to say that every one the category delegates must be weak properies, otherwise you’ll create a extremely unhealthy reatin cycle. 😱
protocol InputDelegate: class { }
class InputHandler {
weak var delegate: InputDelegate?
}
class InputReceiver: InputDelegate {
}Right here is the altered Swift code snippet, however now utilizing a category because the delegate. You simply have to vary your protocol just a little bit and the property contained in the delegator. At all times use weak delegate variables if you’ll assign a category as a delegate. ⚠️
As you may see delegation is fairly simple, however it may be harmful. It helps decoupling by offering a standard interface that can be utilized by anybody who implements the delegate (typically information supply) protocol. There are actually superb articles about delegates, if you would like to know extra about this sample, it is best to verify them out.
