viewController.swift

import UIKit
import RacoonKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        //How to add subviews.
        let firstView = UIView()
        let secondView = UIView()
        let thirdView = UIView()
        let fourthView = UIView()
        view.addSubviews(views: firstView, secondView, thirdView, fourthView)
    }
}