Typical Stevia/ViewController use case

ViewController.swift

//
//  ViewController.swift
//  steviademo
//
//  Created by Onur Geneş on 17.07.2018.
//  Copyright © 2018 Onur Geneş. All rights reserved.
//

import UIKit
import Stevia

class ViewController: UIViewController {
    
    let v = View()
    override func loadView() { view = v }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        v.textField.delegate = self
        
        // Plug tap events.
        v.addButton.addTarget(self, action: #selector(handleKeyboard), for: .touchUpInside)
        v.sendButton.addTarget(self, action: #selector(handleKeyboardDismiss), for: .touchUpInside)
    
        // Register for keyboard events.
        let nc = NotificationCenter.default
        nc.addObserver(self, selector: #selector(keyboardWillShowAnimation), name: .UIKeyboardWillShow, object: nil)
        nc.addObserver(self, selector: #selector(keyboardWillHideAnimation), name: .UIKeyboardWillHide, object: nil)
    }
    
    @objc
    func handleKeyboard() {
        v.textField.becomeFirstResponder()
    }
    
    @objc
    func handleKeyboardDismiss() {
        v.textField.resignFirstResponder()
    }
    
    // MARK - Keyboard management
    
    @objc
    func keyboardWillShowAnimation(notification: Notification) {
        guard let keyboardRect = (notification.userInfo![UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue else  { return }
        let collectionViewHeight = v.collectionView.frame.height
        animateBottomViewWith(offset: keyboardRect.height - collectionViewHeight )
    }
    
    @objc
    func keyboardWillHideAnimation(notification: Notification) {
        animateBottomViewWith(offset: 0)
    }
    
    private func animateBottomViewWith(offset: CGFloat) {
        v.bottomView.bottomConstraint?.constant = offset
        UIView.animate(withDuration: 0.5) {
            self.view.layoutIfNeeded()
        }
    }
}

extension ViewController: UITextFieldDelegate {
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        view.endEditing(true)
        return true
    }
}