HabitsView.swift

import UIKit

protocol HabitsViewDelegate: class {
    func habitsView(_ habitsView: HabitsView, didSelectAddButton button: UIButton)
}

class HabitsView: UIView {

    weak var delegate: HabitsViewDelegate?

    private lazy var tableView: UITableView = {
        let tableView = UITableView()
        tableView.translatesAutoresizingMaskIntoConstraints = false

        return tableView
    }()

    private lazy var addButton: AddButton = {
        let button = AddButton()
        button.addTarget(self, action: #selector(addButtonAction(button:)), for: .touchUpInside)
        button.translatesAutoresizingMaskIntoConstraints = false

        return button
    }()

    override init(frame: CGRect) {
        super.init(frame: frame)

        addSubviewsAndConstraints()
    }

    required init?(coder _: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    private func addSubviewsAndConstraints() {
        addSubview(tableView)
        addSubview(addButton)

        tableView.leftAnchor.constraint(equalTo: leftAnchor).isActive = true
        tableView.heightAnchor.constraint(equalTo: heightAnchor).isActive = true
        tableView.rightAnchor.constraint(equalTo: rightAnchor).isActive = true

        addButton.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -16).isActive = true
        addButton.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: -16).isActive = true
        addButton.widthAnchor.constraint(equalToConstant: 50).isActive = true
        addButton.heightAnchor.constraint(equalToConstant: 50).isActive = true
    }

    @IBAction func addButtonAction(button: UIButton) {
        delegate?.habitsView(self, didSelectAddButton: button)
    }
    
}

The controller is like this:

class HabitsController: UIViewController {

    lazy var addHabitController: AddHabitController = {
        let addHabitController = AddHabitController()
        addHabitController.modalTransitionStyle = .crossDissolve
        // addHabitController.delegate = self

        return addHabitController
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func loadView() {
        let view = HabitsView(frame: UIScreen.main.bounds)
        view.delegate = self
        self.view = view
    }
}

extension HabitsController: HabitsViewDelegate {

    func habitsView(_: HabitsView, didSelectAddButton _: UIButton) {
        present(addHabitController, animated: true)
    }
}

Ideally I would set the delegate the same place I set the HabitsViewDelegate.