OneTime Code SwiftUI Wrapper Customizable View

PassCodeCodeView.swift

struct PassCodeCodeView: UIViewRepresentable {
    init(_ count: Int = 5,
         width: CGFloat,
         height: CGFloat,
         spacing: CGFloat = 10,
         action: @escaping (String) -> ()) {
        self.width = width
        self.height = height
        self.spacing = spacing
        self.action = action
        
        for i in 1...count {
            let field = UITextField()
            field.tag = i
            fields.append(field)
        }
    }
    
    let width: CGFloat
    let height: CGFloat
    let spacing: CGFloat

    var action: (String) -> ()
    private var fields: [UITextField] = []// [UITextField]()
    private var fieldsCount: Int { fields.isEmpty ? 1 : fields.count }
    
    private var estimatedFieldWidth: CGFloat {
        let estimation = width - spacing*CGFloat(fieldsCount-1)
        return estimation / CGFloat(fieldsCount)
    }
    
    private var estimatedFieldHeight: CGFloat {
        height // - 5
    }
    
    func beautifyFields(_ fields: [UITextField])  {
        for field in fields {
            field.placeholder = ""
            field.clearButtonMode = .whileEditing
            field.textColor = .label
            field.font = .systemFont(ofSize: 20, weight: .bold)
            field.textAlignment = .center
            field.autocorrectionType = .no
            field.clearButtonMode = .never
            field.autocapitalizationType = .none
            field.textContentType = .oneTimeCode
            field.keyboardType = .numberPad
            field.heightAnchor.constraint(equalToConstant: estimatedFieldHeight).isActive = true
            field.widthAnchor.constraint(equalToConstant: estimatedFieldWidth).isActive = true
            
            field.layer.borderColor = UIColor.label.cgColor
            field.layer.borderWidth = 1
            field.layer.cornerRadius = 5
        }
    }
    
    func updateTextFields(_ fields: [UITextField]) {
        for field in fields {
            field.layer.borderColor = UIColor.label.cgColor
            field.textColor = .label
        }
    }
    
    func makeUIView(context: Context) -> UIStackView {

        fields.forEach { $0.delegate = context.coordinator }
        beautifyFields(fields)
        //Stack View
        let stackView   = UIStackView()
        stackView.axis  = .horizontal
        stackView.distribution  = .equalSpacing
        stackView.alignment = .center
        stackView.spacing   = spacing
        

        fields.forEach({ stackView.addArrangedSubview($0) })
        
        stackView.translatesAutoresizingMaskIntoConstraints = false
        
        return stackView
        
    }
    
    func updateUIView(_ uiViewController: UIStackView, context: Context) {
        updateTextFields(fields)
    }
    
    func makeCoordinator() -> PassCodeCodeView.Coordinator {
        Coordinator(parent: self)
    }
    
    class Coordinator: NSObject, UITextFieldDelegate {
        var parent: PassCodeCodeView
        
        init(parent: PassCodeCodeView) {
            self.parent = parent
        }
        
        
        func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
            if !(string == "") {
                textField.text = string
                for i in (0..<parent.fields.count) {

                    if textField == parent.fields.last {
                        textField.resignFirstResponder()
                        
                        let inputDigits = parent.fields.compactMap(\.text)

                        let passCode = inputDigits.joined()
                        if passCode.count == parent.fieldsCount {
                            parent.action(passCode)
                        }
                        break
                    } else  if textField == parent.fields.fiedAt(i) {
                        parent.fields.fiedAt(i+1)?.text = ""
                        parent.fields.fiedAt(i+1)?.becomeFirstResponder()
                        break
                    }

                }
                

                return false
            }
            else {
                if string.count == 0 && range.length > 0 {
                    textField.text = ""
                    for i in (0..<parent.fields.count).reversed() {
                        if textField == parent.fields.fiedAt(i) {
                            parent.fields.fiedAt(i-1)?.becomeFirstResponder()
                            break
                        }
                    }
                    
                    return false
                }
            }
            return true
        }
        
        func textFieldShouldBeginEditing(_ textField: UITextField) -> Bool {
            if (textField.text?.count ?? 0) > 0 {
                
            }
            return true
        }
    }
    
}

/// Use these extensions with precaution, (e.g: when you're sure that the array is not empty.)
private extension Array where Element == UITextField {
    func fiedAt(_ index: Index) -> UITextField? {
        if indices.contains(index) {
            return self[index]
        } else  {
            return nil
        }
    }
}