You could make a protocol and extend it.

Something like:

protocol Animations {    func animateHidden(flag: Bool)}extension Animations {    func animateHidden(flag: Bool) {        // some code    }}extension UILabel: Animations {}extension UIImageView: Animations {}

Your method will be available for the extended classes:

let l = UILabel()l.animateHidden(false)let i = UIImageView()i.animateHidden(false)

In a comment, you've asked: "in this case how to call self for UILabel and UIImageView in animateHidden function?". You do that by constraining the extension.

Example with a where clause:

extension Animations where Self: UIView {    func animateHidden(flag: Bool) {        self.hidden = flag    }}

Thanks to @Knight0fDragon for his excellent comment about the where clause.

Best Method to Extend UILabel & UIImageView Together

Swift 4.1 / Xcode 9.4

A much better way to do this in your case would be to just extend UIView. This works because both UILabel and UIImageView both inherit from UIView.

Extension

extension UIView {    func animateHidden(flag: Bool) {        self.hidden = flag    }}

Usage of animateHidden(flag: Bool) Extension

Declaration of label and imageView:

label = UILabel()imageView = UIImageView()

Actual usage of extension

label.animateHidden(flag: true)imageView.animateHidden(flag: false)

Bonus - Other Classes that many UI Components Conform to

If you would like to have your extension be able to conform with many different types of UI components, there are 4 types that a very large amount of UI components conform to:

1. CVarArg
2. Equatable
3. Hashable
4. NSCoding

Some of the many UI components include:

• UILabel: CVarArg, Equatable, Hashable, NSCoding

• UITextField: CVarArg, Equatable, Hashable, NSCoding

• UITableViewCell: CVarArg, Equatable, Hashable, NSCoding

• UITextView: CVarArg, Equatable, Hashable, NSCoding

• UITableView: CVarArg, Equatable, Hashable, NSCoding

• UIImage: CVarArg, Equatable, Hashable, NSCoding

• UIPickerView: CVarArg, Equatable, Hashable, NSCoding

• UIView: CVarArg, Equatable, Hashable, NSCoding

• UIImageView: CVarArg, Equatable, Hashable, NSCoding

• UINavigationBar: CVarArg, Equatable, Hashable, NSCoding

• UIButton: CVarArg, Equatable, Hashable, NSCoding

• UIBarButtonItem: CVarArg, Equatable, Hashable, NSCoding

• UIStackView: CVarArg, Equatable, Hashable, NSCoding

• UIToolbar: CVarArg, Equatable, Hashable, NSCoding

• UITabBar: CVarArg, Equatable, Hashable, NSCoding

• UITabBarItem: CVarArg, Equatable, Hashable, NSCoding

• UIScrollView: CVarArg, Equatable, Hashable, NSCoding

• UISplitViewController: CVarArg, Equatable, Hashable, NSCoding

• UIViewController: CVarArg, Equatable, Hashable, NSCoding

• UIScreen: CVarArg

• UISwitch: CVarArg, Equatable, Hashable, NSCoding

• UISlider: CVarArg, Equatable, Hashable, NSCoding

• UIAlertAction: CVarArg

• UIAlertController: CVarArg, Equatable, Hashable, NSCoding

• UIImageAsset: CVarArg, Equatable, Hashable, NSCoding

• UIDatePicker: CVarArg, Equatable, Hashable, NSCoding

• UINib: CVarArg

• UIResponder: CVarArg

• UIWindow: CVarArg, Equatable, Hashable, NSCoding

• UIRegion: CVarArg, Equatable, Hashable, NSCoding

• UIControl: CVarArg, Equatable, Hashable, NSCoding

• UIBezierPath: CVarArg, Equatable, Hashable, NSCoding

• UIVisualEffect: CVarArg, Equatable, Hashable, NSCoding

• UISearchBar: CVarArg, Equatable, Hashable, NSCoding

• UIMenuItem: CVarArg

• UIMenuController: CVarArg

• UIStoryboard: CVarArg

• And many more...

This means that by extending either CVarArg, Equatable, Hashable, or NSCoding, you can extend most (if every not every) UI component.

Well anyways, I hope this all helps you resolve your issue and if you have absolutely any questions, suggestions, etc., feel free to ask!