IPLookup is the one singleton class of the dropdown. It is very easy to manage dropdown in using single file. configuration is in the same place so easy to modify when the requirement changes. :)

IPLookup.swift

//
//  Lookup.swift
//
//
//  Created by Ilesh's 2018 on 09/03/19.
//  Copyright © 2019 Ilesh. All rights reserved.
//

import Foundation

/*
Add pod file for the dropdown list
 
  pod 'DropDown'
 
 Check here full details for pods

 https://github.com/AssistoLab/DropDown

*/
import DropDown

class Lookup {
    static let shared : Lookup = Lookup()
    
    //LIST
    //let dropDown = DropDown()
    lazy var dropDown : DropDown = {
        let newDropDown = DropDown()
        let appearance = DropDown.appearance()
        appearance.cellHeight = 40
        appearance.backgroundColor = UIColor(white: 1, alpha: 1)
        appearance.selectionBackgroundColor = UIColor(red: 0.6494, green: 0.8155, blue: 1.0, alpha: 0.2)
        //        appearance.separatorColor = UIColor(white: 0.7, alpha: 0.8)
        appearance.shadowColor = UIColor(white: 0.6, alpha: 1)
        appearance.animationduration = 0.25
        appearance.textColor = UIColor.label.red
        //        appearance.textFont = UIFont(name: "Georgia", size: 14)
        
        if #available(iOS 11.0, *) {
            appearance.setupMaskedCorners([.layerMaxXMaxYCorner, .layerMinXMaxYCorner])
        }
        
        /*newDropDown.cellNib = UINib(nibName: "AddLabelCell", bundle: nil)
        
        newDropDown.customCellConfiguration = { (index: Index, item: String, cell: DropDownCell) -> Void in
            guard let cell = cell as? AddLabelCell else { return }
            // Setup your custom UI components
            //cell.viewLabel.backgroundColor = UIColor.hexString(self.arrColorLabel[index])
            cell.viewLabel.layer.cornerRadius = cell.viewLabel.frame.height / 2
            cell.viewLabel.layer.masksToBounds = true
        }*/
        return newDropDown
    }()
    
    func show(view:UIView,data:[String], selection: @escaping (_ index:Int,_ item:String) -> Void ) {
        dropDown.anchorView = view
        dropDown.bottomOffset = CGPoint(x: 0, y: view.bounds.height)
        dropDown.dataSource = data
        dropDown.selectionAction = { [weak self] (index, item) in
            selection(index,item)
        }
        dropDown.show()
    }
}