Do I need to call DispatchQueue when presenting a ViewController from other ViewControllers

user_1577308 0
Viewed 678

I'm trying to present the UIActivityViewController in multiple parts of my app by enclosing it in a helper class. The following code works fine, I can call the showActivityController() method from any other view controllers in my app, and the UIActivityViewController gets presented as expected.

My question is, do I really need to enclose the code to present the UIActivityViewController within the DispatchQueue.main.async as shown below?

I tried it without it and it works fine but I want to make sure that leaving it there won't cause any issues later on.

class HelperClass: UIViewController, UIActivityItemSource{
    static let shared = HelperClass()

    func showActivityController(){
        DispatchQueue.main.async {
            let items = [self]
            let activityController = UIActivityViewController(activityItems: items, applicationActivities: nil)
            UIApplication.shared.keyWindow?.rootViewController?.present(activityController, animated: true)
        }
    }

    func activityViewControllerPlaceholderItem(_ activityViewController: UIActivityViewController) -> Any {
        return "Return Type"
    }

    func activityViewController(_ activityViewController: UIActivityViewController, itemForActivityType activityType: UIActivity.ActivityType?) -> Any? {
        if activityType == .message{
            return "Text for iMessage"
        }else if activityType == .mail{
            return "Text for Email" 
        }else{
            return "Text for all other apps"
        }
    }
    func activityViewController(_ activityViewController: UIActivityViewController, subjectForActivityType activityType: UIActivity.ActivityType?) -> String {
        return "Email Subject"
    }
}

Usage from other View Controllers

HelperClass.shared.showActivityController()
dispatch-queue uiactivityviewcontroller swift ios
2 Answers

You don't need when you are in main thread only. So writing DispatchQueue is redundant

But in case if you want to present from another thread it will be a must for you presenting the UI using DispathchQueue

Suppose , you are making a network call and and after the completion of network call you have to show UI

From my point of view, you should remove the dispatch queue from the method. 

func showActivityController(){
         let items = [self]
            let activityController = UIActivityViewController(activityItems: items, applicationActivities: nil)
            UIApplication.shared.keyWindow?.rootViewController?.present(activityController, animated: true)
    }

But when you have to present the UI from other thread, just call the method in main thread

DispatchQueue.main.async {
    HelperClass.shared.showActivityController()   
}
user_84756380

Better to keep all interface related code on the main thread, so I would leave it with the DispatchQueue.main.async as at some point you can call showActivityController() from closure that is executed on a background thread causing runtime error. Calling DispatchQueue.main.async is safer and not causing any overhead until you call this method million times in a row.

user_21497790
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