Show UIPickerView like a keyboard, without UITextField

Question

I\'m looking for a way to present a UIPickerView when the user taps on a UIBarButtonItem. Imagine a filter for the table view results.

I know I

Answer 1

I went with borisgolovnev's suggestion of an invisible UITextField and came up with the following Swift 2.3 implementation:

import UIKit

class PickerViewPresenter: UITextField {

    // MARK: - Initialization

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

    init() {
        super.init(frame: CGRect.zero)
    inputView = pickerView
    inputAccessoryView = pickerInputAccessoryView
    }

    // MARK: - Public

    var pickerDelegate: UIPickerViewDelegate? {
        didSet {
            pickerView.delegate = pickerDelegate
        }
    }

    var pickerDataSource: UIPickerViewDataSource? {
        didSet {
            pickerView.dataSource = pickerDataSource
        }
    }

    var selectButtonAction: (() -> Void)?

    var currentlySelectedRow: Int {
        return pickerView.selectedRowInComponent(0)
    }

    func selectRowAtIndex(index: Int) {
        pickerView.selectRow(index, inComponent: 0, animated: false)
    }

    func showPicker() {
        self.becomeFirstResponder()
    }

    func hidePicker() {
        self.resignFirstResponder()
    }

    // MARK: - Views

    private let pickerView = UIPickerView(frame: CGRect.zero)

    private lazy var pickerInputAccessoryView: UIView = {
        let frame = CGRect(x: 0.0, y: 0.0, width: 0.0, height: 48.0)
        let pickerInputAccessoryView = UIView(frame: frame)

        // Customize the view here

        return pickerInputAccessoryView
    }()

    func selectButtonPressed(sender: UIButton) {
        selectButtonAction?()
    }

}

PickerViewPresenter can then conveniently be used as such:

class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(pickerViewPresenter)
    }

    private let dataModel = [10, 20, 30, 40, 50]

    private lazy var pickerViewPresenter: PickerViewPresenter = {
        let pickerViewPresenter = PickerViewPresenter()
        pickerViewPresenter.pickerDelegate = self
        pickerViewPresenter.pickerDataSource = self
        pickerViewPresenter.selectButtonAction = { [weak self] () -> Void in
            guard let strongSelf = self else {
                return
            }
            let result = strongSelf.dataModel[pickerViewPresenter.currentlySelectedRow]
            pickerViewPresenter.hidePicker()
            // ...
        }

        return pickerViewPresenter
    }()

    private func presentPickerView {
        let index = 0 // [0..dataModel.count-1]
        pickerViewPresenter.selectRowAtIndex(index)
        pickerViewPresenter.showPicker()
    }

    // MARK: - UIPickerViewDataSource

    func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
        return 1
    }

    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return dataModel.count
    }

    // MARK: - UIPickerViewDelegate

    func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return "\(dataModel[row]) drunken sailors"
    }

}

Hope someone finds this useful =)