Using Protocol Extension Constraint

Dao.swift

import Foundation
import UIKit

protocol Dao {}
extension NSObject: Dao {}

extension Dao where Self : NSObject {
    
    typealias ConfigClosure = (Self) -> Void
    
    init(_ closures: ConfigClosure...) {
        self.init()
        
        closures.forEach {
            $0(self)
        }
    }
}

let btn = UIButton() {
     $0.frame = CGRect(x: 10, y: 10, width: 44, height: 44)
     $0.backgroundColor = .red
 }
 print(btn)
 
// or 

 let simplifyBtn = UIButton {
     $0.frame = CGRect(x: 10, y: 10, width: 44, height: 44)
     $0.backgroundColor = .red
 }
 print(simplifyBtn)
 
 let dic = NSMutableDictionary {
     $0["key"] = 10
 }