“Unrecognized selector sent to instance” in UIView class when calling addTarget

Question

I am trying to create a DropDownMenu class, but when I try to call addTarget to one of the buttons, this error comes up.

unrecognized selector sent to instance 0x7fd167f06120' terminating with uncaught exception of type NSException

I would really appreciate any help and no answer is a bad one!

Here is my entire class

class DropDownMenu: UIView {
    // Main button or Pre
    var main: UIButton! = UIButton(frame: CGRect(x: 0, y: 0, width: 46, height: 30))
    var view: UIView!
    
    
    // Title
    var buttonTitles: [String]! = [""]
    var titleColor: UIColor! = UIColor.black
    var font: UIFont! = UIFont.systemFont(ofSize: 18)
    // Individual Button
    var buttonsBorderWidth: CGFloat! = 0
    var buttonsBorderColor: UIColor? = UIColor.white
    var buttonsCornerRadius: CGFloat! = 0
    var color: UIColor! = UIColor.clear
    // Button Images
    var buttonsImageEdgeInsets: UIEdgeInsets? = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
    var images: [UIImage]? = nil
    // Onclick stuff
    var target: UIViewController!
    
    private var currentSelected: String? = nil
    
    private var optionsStack = UIStackView()
    
    init(main: UIButton) {
        self.main = main
        super.init(frame: CGRect())
    }
    
    func createDropDownMenu() {
        main.addTarget(target, action: #selector(DropDownMenu.openDropdown(_:)), for: .touchUpInside)
        
        print("Button Target?: \(main.allTargets), self.target: \(String(describing: target))")
        
        let mainFrame = main.frame
        
        optionsStack.frame = CGRect(x: mainFrame.minX, y: mainFrame.maxY, width: mainFrame.width, height: CGFloat(buttonTitles.count) * mainFrame.height)
        optionsStack.axis = .vertical
        
        view.addSubview(optionsStack)
                
        var y: CGFloat! = 0
        
        for title in buttonTitles {
            let button = UIButton(frame: CGRect(x: 0, y: y, width: mainFrame.width, height: mainFrame.height))
            button.setTitle(title, for: .normal)
            button.setTitleColor(titleColor, for: .normal)
            button.backgroundColor = color
            button.titleLabel?.font = font
            button.addTarget(target, action: #selector(DropDownMenu.onclick), for: .touchUpInside)
            
            y += mainFrame.height
            
            optionsStack.addArrangedSubview(button)
        }
        
        for button in optionsStack.arrangedSubviews {
            button.isHidden = true
            button.alpha = 0
        }
    }
    
    @objc private func openDropdown(_ sender: UIButton) {
        print("sender: \(String(describing: sender))")
        optionsStack.arrangedSubviews.forEach { (button) in
            UIView.animate(withDuration: 0.7) {
                button.isHidden = !button.isHidden
                button.alpha = button.alpha == 0 ? 1 : 0
                self.view.layoutIfNeeded()
            }
        }
    }
    
    @objc private func onclick(_ sender: UIButton) {
        let title = sender.titleLabel!.text
        
        print(title as Any)
        
        main.setTitle(title, for: .normal)
        
        optionsStack.arrangedSubviews.forEach { (button) in
            UIView.animate(withDuration: 0.7) {
                button.isHidden = true
                button.alpha = 0
            }
        }
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

Here is the code and creation of the object in ViewController

let grade = UIButton(frame: CGRect(x: 50, y: 300, width: 80, height: 30))
grade.layer.borderWidth = 1
grade.setTitle("Grade", for: .normal)
grade.titleLabel?.font = UIFont.boldSystemFont(ofSize: 20)
grade.setTitleColor(UIColor.black, for: .normal)
        
let gradeDP = DropDownMenu(main: main)
gradeDP.buttonTitles = ["Title 1", "Title 2", "Title 3"]
gradeDP.color = UIColor.gray
gradeDP.target = self
gradeDP.titleColor = UIColor.white
gradeDP.view = view

view.addSubview(grade)
gradeDP.createDropDownMenu()

The first print statement in the createDropDownMenu() function prints...

Button Target?: [AnyHashable(<HomeworkHelp.DropDownMenu: 0x7ffb555200b0; frame = (0 0; 0 0); layer = <CALayer: 0x600002bdf5c0>>)], self.target: Optional(<HomeworkHelp.CreateAccountViewController: 0x7ffb5550a7b0>)

After editing it with the help of mightknow I came up with this class. It doesn't have any onclick actions for the mainButton in it.

class DropDownMenu: UIStackView {
    
    var options: [String]! = [] // Labels for all of the options
    var titleButton: UIButton! = UIButton() // The Main Title Button
    
    init(options: [String]) {
        self.options = options
        let mainFrame = titleButton.frame
        
        super.init(frame: CGRect(x: mainFrame.minX, y: mainFrame.maxY, width: mainFrame.width, height: mainFrame.height * CGFloat(options.count)))
        
        var y: CGFloat = 0
        for title in self.options {
            let button = UIButton(frame: CGRect(x: 0, y: y, width: self.frame.width, height: mainFrame.height))
            button.setTitle(title, for: .normal)
            button.setTitleColor(titleButton.titleLabel?.textColor, for: .normal)
            button.backgroundColor = titleButton.backgroundColor
            button.addTarget(self, action: #selector(dropDownOptionClicked(_:)), for: .touchUpInside)
            
            button.isHidden = true
            button.alpha = 0
            
            self.addArrangedSubview(button)
            
            y += 1
        }
    }
    
    @objc func openDropDown(_ sender: UIButton) {
        print("Open DropDownMenu")
        for button in self.arrangedSubviews {
            UIView.animate(withDuration: 0.7) {
                button.isHidden = !button.isHidden
                button.alpha = button.alpha == 0 ? 1 : 0
                self.layoutIfNeeded()
                self.superview?.layoutIfNeeded()
            }
        }
    }
    
    @objc private func dropDownOptionClicked(_ sender: UIButton) {
        print(sender.titleLabel?.text as Any)
    }
    
    init() {
        super.init(frame: CGRect.zero)
    }
    
    required init(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

And than my ViewController is ...

let dp = DropDownMenu(options: ["Label 1", "Label 2", "Label 3"])
        
let titleButton = UIButton(frame: CGRect(x: 100, y: 300, width: 180, height: 40))
titleButton.backgroundColor = UIColor.white
titleButton.setTitle("DropDownMenu", for: .normal)
titleButton.setTitleColor(UIColor.black, for: .normal)
titleButton.layer.borderWidth = 2
titleButton.addTarget(self, action: #selector(dp.openDropDown(_:)), for: .touchUpInside)
        
dp.titleButton = titleButton

The error ...

Button Target?: [AnyHashable(<HomeworkHelp.DropDownMenu: 0x7ffb555200b0; frame = (0 0; 0 0); layer = <CALayer: 0x600002bdf5c0>>)], self.target: Optional(<HomeworkHelp.CreateAccountViewController: 0x7ffb5550a7b0>)

still comes up and I am clueless as to why.

Answer 1

I finally figured it out! The target has to be the DropDownMenu.

titleButton.addTarget(dp, action: #selector(dp.openDropDown(_:)), for: .touchUpInside)

Here is the rest of the code...

let titleButton = UIButton(frame: CGRect(x: 50, y: 290, width: 100, height: 40))
titleButton.backgroundColor = UIColor.white
titleButton.setTitle("Grade", for: .normal)
titleButton.setTitleColor(UIColor.black, for: .normal)
titleButton.layer.borderWidth = 2
titleButton.layer.cornerRadius = 10
        
let dp = DropDownMenu(options: ["1", "Freshman", "Sophomore", "Junior", "Senior", "College"])
dp.titleButton = titleButton
dp.target = self
dp.borderWidth = 2
dp.spacing = 5
dp.cornerRadius = 10
dp.bgColor = UIColor.white

Adding it to subviews and creating it...

view.addSubview(titleButton)
view.addSubview(dp)
dp.createDropDownMenu()

Answer 2

As for suggestions with rebuilding your class so it works properly, you may want to start with something like this:

class DropDownMenu : UIView {

var dropdownOptions : [String] = []
private var titleButton : UIButton = UIButton()
private var optionsStack : UIStackView = UIStackView()
private var optionsButtons : [UIButton] = []

@objc private func openDropdown(_ sender: UIButton) {
    // Add code to make dropdown options appear. There are multiple ways of doing this. For instance, the optionsButtons could be hidden and then unhidden when it's clicked, or they could be created only once the button is clicked.
}

@objc private func selectedOption(_ sender: UIButton) {
    // Code here for when option is selected
}

init(options: [String]) {
    self.dropdownOptions = options
    super.init(frame: CGRect.zero)
    // Customize all of your subviews here, and add them to your DropDownMenu (as subviews)
    // Add openDropdown(_:) target to self.titleButton
}

required init?(coder: NSCoder) {
    super.init(coder: coder)
}
}

A lot of the code you have already written for your original version of the class can go inside the functions there. Also, there is a lot of unnecessary code in your original version. For example, the target variable is unused once you fixed the original error issue, the view variable is obsolete, and the createDropDownMenu() function is unnecessary because all of that code can go either in the init(options:) or openDropdown(_:) functions.

Then, if you choose to build out a class using that template, you would implement it in your ViewController's viewDidLoad() method with the code:

let dropdown = DropDownMenu(titles: ["Title 1", "Title 2", "Title 3"])
self.view.addSubview(dropdown)
// Follow that with layout code that ensures it's the proper size and in the proper location

I hope that combined with my comments make sense, are helpful, and aren't too overwhelming. What I recommend doing is starting a new empty project (or target) and building your class and adding it to a ViewController with nothing else in it. That's a good way to isolate it and check and make sure everything looks and works right. In case you want an alternate suggestion with how to build your class, you can actually try making DropDownMenu be a subclass of UIStackView (instead of UIView) with the main button and all option buttons being arranged subviews. This might actually be simpler, because it kind of cuts out the middleman, if you will, and all you'd need to do when opening/closing the dropdown is add/remove views from the .arrangedSubviews property.

Also important is that if your view needs to pass information (such as which option is selected) back to the ViewController, make sure the reference to the ViewController is marked weak so you don't create a retain cycle.

On a final note, if you're disappointed that there isn't a quick fix to get the original class to work and want to keep trying at that, there might be some way to cobble together a solution (like the code from my first answer, which does actually work...), but ultimately it will probably only cause more issues further down the line. So, best of luck with everything.

Answer 3

You're setting the target as a UIViewController when the method you're calling is actually a method of the DropDownMenu class. What you need to do is set the target to self instead of the target property:

main.addTarget(self, action: #selector(DropDownMenu.openDropdown(_:)), for: .touchUpInside)

EDIT: In response to your comment, here is the code I'm using to test it. There are some layout/color choices I made just to make it clear to me, but this works:

class ViewController: UIViewController {
override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    let main = UIButton(frame: CGRect(x: 0, y: 100, width: 80, height: 30))
    main.layer.borderWidth = 1
    main.setTitle("Grade", for: .normal)
    main.titleLabel?.font = UIFont.boldSystemFont(ofSize: 20)
    main.setTitleColor(UIColor.black, for: .normal)
            
    let gradeDP = DropDownMenu(main: main)
    gradeDP.buttonTitles = ["Title 1", "Title 2", "Title 3"]
    gradeDP.color = UIColor.gray
    gradeDP.target = self
    gradeDP.titleColor = UIColor.white
    gradeDP.view = UIView()
    
    self.view.addSubview(gradeDP)
    let b = self.view.bounds
    gradeDP.frame = CGRect(x: b.minX, y: b.minY, width: b.width, height: b.height/2)
    gradeDP.backgroundColor = UIColor.purple
    gradeDP.target = self
    gradeDP.addSubview(gradeDP.main)
    gradeDP.createDropDownMenu()
}}

As for your code, I'm going on the assumption that the code you added in the second part of your question is inside your ViewController's viewDidLoad() method, and that the main variable you're using to initialize your DropDownMenu is an instance variable of your ViewController, because I'm not seeing it anywhere else in scope. If that's the case, there are definitely some issues. They are:

1. You never actually add gradeDP to your view hierarchy. If that's what the line gradeDP.view = view is supposed to do, it's not. What that code actually does is set the view property of gradeDP to be a reference to the ViewController's view property. And, unless there is code in your DropDownMenu class that you haven't included, you're not actually using that reference for anything. So, you can get rid of that line entirely, and the view property in your DropDownMenu class. If what you're trying to do is set the ViewController's view to be gradeDP, that code would be self.view = gradeDP, but I don't actually recommend doing it that way. A UIViewController's view property is used in some special functionality and probably shouldn't be messed with much. You probably want to add gradeDP as a subview, like I did in my code above.

2. The grade button you created is not used by your DropDownMenu. I'm guessing you meant to initialize with that instead of the main variable (that is out of scope of your code), like this:

   let gradeDP = DropDownMenu(main: grade)

In short, unless there is code elsewhere that you haven't shared, what your code above does is create a UIButton labeled "Grade" that is visible but doesn't actually do anything (and isn't part of your DropDownMenu), and a DropDownMenu that isn't actually visible, but would have a main button that calls openDropdown(_:) if it was. I'm guessing that's not how it's supposed to work. Hopefully the code I provided above helps get you where you want to be, though.