Protocol method does not pass the correct parameter - ios

Question

Consider this case, suppose you have a subclass of UIView and a protocol i.e.
protocol MyViewProtocol
{
func didTapSelf(thisView: MyView)
}
class MyView: UIView
{
lazy var tf: UITextField =
{
let obj = UITextField()
obj.translatesAutoresizingMaskIntoConstraints = false
obj.placeholder = "Enter text"
obj.backgroundColor = .white
return obj
}()
var btn: UIButton =
{
let obj = UIButton()
obj.translatesAutoresizingMaskIntoConstraints = false
obj.addTarget(self, action: #selector(didTapBtn), for: .touchUpInside)
obj.backgroundColor = .orange
return obj
}()
var delegate: MyViewProtocol?
init(backgroundColor: UIColor, placeholder: String, delegate: MyViewProtocol?)
{
super.init(frame: .zero)
self.backgroundColor = backgroundColor
self.delegate = delegate
tf.placeholder = placeholder
configureUI()
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configureUI()
{
addAllSubviews(tf,
btn)
NSLayoutConstraint.activate([
btn.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 12),
btn.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -12),
btn.topAnchor.constraint(equalTo: topAnchor, constant: 32),
tf.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 12),
tf.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -12),
tf.topAnchor.constraint(equalTo: btn.bottomAnchor, constant: 12),
tf.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -12),
tf.heightAnchor.constraint(equalToConstant: 44)
])
// let gesture = UITapGestureRecognizer(target: self, action: #selector(didTapBtn))
// gesture.cancelsTouchesInView = false
// addGestureRecognizer(gesture)
}
#objc func didTapBtn()
{
delegate?.didTapSelf(thisView: self)
}
}
Now, inside your view controller, make 2 instances of MyView i.e.
lazy var myView1: MyView =
{
let obj = MyView(backgroundColor: .yellow, placeholder: "view 1", delegate: self)
obj.translatesAutoresizingMaskIntoConstraints = false
return obj
}()
lazy var myView2: MyView =
{
let obj = MyView(backgroundColor: .green, placeholder: "view 2", delegate: self)
obj.translatesAutoresizingMaskIntoConstraints = false
return obj
}()
And implement your view controller with the protocol method like this:
extension ViewController: MyViewProtocol
{
func didTapSelf(thisView: MyView)
{
if thisView == myView1
{
print("tapped view 1")
}
else if thisView == myView2
{
print("tapped view 2")
}
else
{
print("i am ambigious")
}
}
}
Now when you tap the button in myView1 or myView2 it will print correctly, i.e. tapped view 1 or 2, whichever button is tapped, but as you start editing the myView1 textField and for time when it is in editing state, no matter whichever button of myView1 or myView2 you tap, it will only print tapped view 1, or whatever view, whose textField is in editing mode.
For my knowledge, it must pass the correct self object, regardless of the editing state of textField . Why is this behaviour occurring ?
p.s this behaviour does not occur when you use a tap gesture on any of above views.

Answer 1

This has nothing to do, really, with the protocol or any of the other red herrings in the story. A little debugging will reveal that in fact the correct button is being tapped, but the runtime is literally sending the target–action message to the wrong MyView. The underlying reason is that in this line:
obj.addTarget(self, action: #selector(didTapBtn), for: .touchUpInside)
... the term self doesn't mean what you think it does.
To fix the issue, simply change
var btn: UIButton =
To
lazy var btn: UIButton =