Using image as gesture recognizer in Swift/Xcode, image coming up nil - ios

Question

I just got finished going through the big nerd ranch iOS programming book and started my first 'project'. I'm trying to use a UIImageView as a button but my image is coming up as nil and I cannot figure out why. I'm new at this, so any help, or even just identifying any parts of this code that don't make sense is appreciated.
import UIKit
class ImageScreenViewController: UIViewController {
# IBOutlet var imageView: UIImageView!
// set up images
let picture1 = UIImage(named: "picture1")
override func viewDidLoad() {
super.viewDidLoad()
// set image on screen
imageView.image = picture1
}
// set up gesture recognizer
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
let tapRecognizer = UITapGestureRecognizer(target: self, action: #selector(count(_:)))
self.imageView.addGestureRecognizer(tapRecognizer)
self.imageView.isUserInteractionEnabled = true
}
#objc func count(_ gestureRecognizer: UIGestureRecognizer) {
print("tapped the picture")
}
}
note, picture1 is in Assets.xcassets.

Answer 1

Some explanation for your question
encodeWithCoder(_ aCoder: NSCoder) {
// Serialize
}
init(coder aDecoder: NSCoder) {
// Deserialize
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
//You used
}
To add a Gesture you actually do not need to implement coder here as These are being used to store the state
Check following example
1- ImageView is being taken from storyBoard
2- myImage is being Added using code
Now , Storyboard initially implants serialise and deserialise mechanism
Thus imageView is a property being added from storyboard so no need for coder there
import UIKit
class ImageVC: UIViewController {
# IBOutlet var imageView: UIImageView!
// set up images
let picture1 = UIImage(named: "cc")
//ImageView programmaticlly
var myImage = UIImageView()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
// set image on screen
imageView.image = picture1
//setting properties and frame
myImage.image = picture1
myImage.frame = CGRect(x: 0, y: 0, width: 100, height: 100)
self.view.addSubview(myImage)
let tapRecognizer = UITapGestureRecognizer(target: self, action: #selector(count(_:)))
self.imageView.addGestureRecognizer(tapRecognizer)
self.imageView.isUserInteractionEnabled = true
}
// set up gesture recognizer
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
//adding gesture
let tapRecognizer = UITapGestureRecognizer(target: self, action: #selector(count(_:)))
self.myImage.addGestureRecognizer(tapRecognizer)
self.myImage.isUserInteractionEnabled = true
}
#objc func count(_ gestureRecognizer: UIGestureRecognizer) {
print("tapped the picture")
}
}
As if you implement above Algo It won't crash , as For Properties being added from storyboard can directly be accessed in didload or willAppear as we never going to remove them from superview so indirectly its serialised
Second case - myImage - Added Programmatically can also be removed from superView and added again Thus can be serialised means need to be

Answer 2

you can add tapRecongnize in viewDidload because in init method imageview not initialize and return nil so that you can use like this
override func viewDidLoad() {
super.viewDidLoad()
imageView.image = picture1
let tapRecognizer = UITapGestureRecognizer(target: self, action: #selector(count(_:)))
self.imageView.addGestureRecognizer(tapRecognizer)
self.imageView.isUserInteractionEnabled = true
}

Answer 3

var image: UIImage?
#IBOutlet weak var imageChoisie: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
imageChoisie.image = image // from Segue
// Click on Image
let tapRecognizer = UITapGestureRecognizer(target: self, action: #selector(count(_:)))
self.imageChoisie.addGestureRecognizer(tapRecognizer)
self.imageChoisie.isUserInteractionEnabled = true
}
#objc func count(_ gestureRecognizer: UIGestureRecognizer) {
//print("tapped the picture")
dismiss(animated: true, completion: nil) // back previous screen
}