Custom action for a specific share types

MyCustomShare.swift

//
// custom action for a specific share types
//

class MyCustomShare: NSObject, UIActivityItemSource {
    
    static func share() {
        
        let vc = UIViewController.topViewController()
        
        let activityViewController = UIActivityViewController(activityItems: [self], applicationActivities: nil)
        activityViewController.popoverPresentationController?.sourceView = vc?.view
        vc?.present(activityViewController, animated: true, completion: nil)
    }
    
    // MARK: - UIActivityItemSource Protocol

    func activityViewController(_ activityViewController: UIActivityViewController, itemForActivityType activityType: UIActivityType?) -> Any? {
        
        var message: String = "you custom message"
        
        if activityType == UIActivityType.postToFacebook {
            activityViewController.dismiss(animated: false) {
                
                // TODO: your custom actions
                
            }
            
            return nil
        }
        
        return message

    }

    
    func activityViewController(_ activityViewController: UIActivityViewController, subjectForActivityType activityType: UIActivityType?) -> String {
        
        return "your subject" // form email
    }
    
    func activityViewController(_ activityViewController: UIActivityViewController, thumbnailImageForActivityType activityType: UIActivityType?, suggestedSize size: CGSize) -> UIImage? {
        
        var image: UIImage?
        
        if let imageUlr = "your image url", let url = URL(string: imageUlr) {
            guard let data = try? Data(contentsOf: url) else {
                return nil
            }
            
            image = UIImage(data: data)
        }
        
        return image
    }
    
    func activityViewControllerPlaceholderItem(_ activityViewController: UIActivityViewController) -> Any {
        return ""
    }
    
}

extension UIViewController {
    
    static var root: UIViewController? {
        get {
            return UIApplication.shared.delegate?.window??.rootViewController
        }
    }
    
    static func topViewController(from viewController: UIViewController? = UIViewController.root) -> UIViewController? {
        if let tabBarViewController = viewController as? UITabBarController {
            return topViewController(from: tabBarViewController.selectedViewController)
        } else if let navigationController = viewController as? UINavigationController {
            return topViewController(from: navigationController.visibleViewController)
        } else if let presentedViewController = viewController?.presentedViewController {
            return topViewController(from: presentedViewController)
        } else {
            return viewController
        }
    }

    
}