Created
April 14, 2017 18:27
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Dangers of implicitly unwrapped optionals
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//: Playground - noun: a place where people can play | |
import UIKit | |
import PlaygroundSupport | |
class ViewController: UIViewController { | |
lazy var tapHandler: TapHandler = TapHandler(delegate: self, view: self.view) | |
} | |
extension ViewController: TapHandlerDelegate { | |
func handleTap() { | |
} | |
} | |
protocol TapHandlerDelegate: class { | |
func handleTap() | |
} | |
class TapHandler { | |
weak var delegate: TapHandlerDelegate! | |
init() { | |
} | |
init(delegate: TapHandlerDelegate, view: UIView) { | |
self.delegate = delegate | |
let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(tapReceived)) | |
view.addGestureRecognizer(tapGestureRecognizer) | |
} | |
@objc func tapReceived() { | |
self.delegate.handleTap() | |
} | |
} | |
var tapHandler = TapHandler() | |
autoreleasepool { | |
let viewController = ViewController() | |
tapHandler = viewController.tapHandler | |
print(tapHandler.delegate) //prints the viewController | |
} | |
print(tapHandler) | |
print(tapHandler.delegate) // crashes |
You could also change the last line to tapHandler.handleTap()
which would make it more 'real world'
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Yep, this shows the problem.