为UISearchBar textField添加下边框

if let textField = searchBar.value(forKey: "searchField") as? UITextField {
    // 在这里进行下边框的设置
}

textField.borderStyle = .none  // 取消默认的边框样式
textField.layer.masksToBounds = true
textField.layer.borderColor = UIColor.gray.cgColor  // 设置边框颜色
textField.layer.borderWidth = 1.0  // 设置边框宽度

textField.leftView = UIView(frame: CGRect(x: 0, y: 0, width: 10, height: textField.frame.height))  // 左边距
textField.leftViewMode = .always
textField.rightView = UIView(frame: CGRect(x: 0, y: 0, width: 10, height: textField.frame.height))  // 右边距
textField.rightViewMode = .always