`FileManager.url(forUbiquityContainerIdentifier:)` should not be called from main thread

[aamct2]

Summary

FileManager.url(forUbiquityContainerIdentifier:) is currently being called on the main thread, against Apple's guidance.

Details

At the moment you are instantiating the shared DocumentManager in the DocumentBrowserViewController.viewDidLoad (), which is happening on the main thread.

textor/Textor/Controller/DocumentBrowserViewController.swift

Lines 11 to 17 in f97306e

	class DocumentBrowserViewController: UIDocumentBrowserViewController {
	override func viewDidLoad() {
	super.viewDidLoad()
	// Makes sure everything is initialized
	_ = DocumentManager.shared

When you step through the initialisation of the DocumentManager, you eventually get to a call for the cloudDocumentsURL property which is where the call to FileManager.url(forUbiquityContainerIdentifier:) happens.

textor/Textor/Util/DocumentManager.swift

Lines 60 to 66 in f97306e

	private var cloudDocumentsURL: URL? {
	guard iCloudAvailable else {
	return nil
	}
	let ubiquityContainerURL = fileManager.url(forUbiquityContainerIdentifier: ICLOUD_IDENTIFIER)

This goes against Apple's guidance for FileManager.url(forUbiquityContainerIdentifier:) that it should not be called from the main thread.

Important

Do not call this method from your app’s main thread. Because this method might take a nontrivial amount of time to set up iCloud and return the requested URL, you should always call it from a secondary thread. To determine if iCloud is available, especially at launch time, check the value of the ubiquityIdentityToken property instead.

Link to full Apple documentation: https://developer.apple.com/documentation/foundation/filemanager/1411653-url

[louisdh]

Thanks for pointing this out, I'll take a look.