UIDocumentInteractionController - Show "Quick Look" Option

Question

I am using an instance of UIDocumentInteractionController to offer the user the option to open a given document, if a capable app is installed on their device.

Apple's documentation for the QuickLook Framework mentions that:

To display a Quick Look preview controller you can use any of these options:

• Push it into view using a UINavigationController object.
• Present it modally, full screen, using the presentModalViewController:animated: method of its parent class, UIViewController.
• Present a document interaction controller (as described in Previewing and Opening Files. The user can then invoke a Quick Look preview controller by choosing Quick Look from the document interaction controller’s options menu.

(emphasis mine)

I am opting for that third option: Instead of using a QLPreviewController, I am presenting an UIDocumentInteractionController; this is my code:

@IBAction func openDocument(sender: AnyObject) {

    let interactionController = UIDocumentInteractionController(URL: documentURL)
    interactionController.delegate = self

    // First, attempt to show the "Open with... (app)" menu. Will fail and
    // do nothing if no app is present that can open the specified document
    // type.

    let result = interactionController.presentOpenInMenuFromRect(
        self.view.frame,
        inView: self.view,
        animated: true
    )

    if result == false {
        // Fall back to options view:

        interactionController.presentOptionsMenuFromRect(
            self.view.frame,
            inView: self.view,
            animated: true)
    }
}

The fallback path gets executed (options menu), because I don't have any app that can open docx. However, the mentioned "Quick Look" option is not present:

What am I missing?

---

NOTE: I am not implementing any of the methods of UIDocumentInteractionControllerDelegate.

Answer 1

Silly me... again.

ANSWER: It turns out that, to have the QuickLook option present, you need to implement this method of the delegate protocol:

func documentInteractionControllerViewControllerForPreview(controller: UIDocumentInteractionController) -> UIViewController {
    return self // returning self seems to work
}

(I somehow missed this. On a first read, I thought implementing this method meant that I should return a view controller capable of displaying the content -i.e. a full-fledged docx renderer, in this case. It just asks for a "source" from which to show the preview)

Once I implemented that method, the eye button started to appear in the options menu.

But on clicking it, my app would crash: by the time the quick look launches, the UIDocumentInteractionController was deallocated. I changed it from local variable to property, and now it works.