UISearchBarのテキストフィールド背景色を変える

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UISearchBarのサブビュー内にTextFieldnのviewがあるので、その背景色を変えてあげる

RootViewController.swift

import UIKit

class RootViewController: UIViewController , UISearchBarDelegate{
    
    private var mySearchBar: UISearchBar!
    
    override func viewDidLoad() {
        mySearchBar = UISearchBar()
        mySearchBar.delegate = self
        mySearchBar.frame = CGRectMake(0, 0, self.view.frame.size.width, 44)
        mySearchBar.layer.position = CGPoint(x: self.view.bounds.width/2, y: 32)
        mySearchBar.tintColor = UIColor.darkGrayColor()
        mySearchBar.text = "テスト"
        // 背景色を変える
        for subView in mySearchBar.subviews {
            for secondSubView in subView.subviews {
                if secondSubView.isKindOfClass(UITextField) {
                    secondSubView.backgroundColor = UIColor.lightGrayColor().colorWithAlphaComponent(0.3)
                }
            }
        }
        
        self.navigationItem.titleView = mySearchBar
    }
    
}

参考:　[stackoverflow] Cannot change search bar background color