UITableViewController doesn't seem to refresh when reloadData goes from non-zero to zero sections on iPad

Question

On iPad, in a UISplitViewController, I have a UITableViewController in the right section showing the details of what is selected on the left. So when I deselect everything on the left, consequently setting the detail object to nil in the detail view, I would like the table to clear and to display a message to invite the user to select an element.

That's why I have the following in my detail UITableViewController subclass:

var reference: Reference? {
    didSet {
        self.refreshInterface()
    }
}

func refreshInterface() {
    if let titleLabel = self.titleLabel {
        if let ref = reference {
            titleLabel.text = ref.projectName
        } else {
            titleLabel.text = NSLocalizedString("Please select a reference", comment: "")
        }
    }
    tableView.reloadData()
}

override func numberOfSections(in tableView: UITableView) -> Int {
    if(self.reference != nil) {
        return 5
    } else {
        return 0
    }
}

And I checked with the debugger that after I set the reference to nil, numberOfSections is called and returns 0. But then for some reason, all the UI of the table isn't cleared. I still have the same rows and sections as when I had a reference selected. Am I missing something? Is this a potential bug in Cocoa Touch?

Answer 1

I figured it out. The problem was not in my detail view controller, but in the master one. I didn't take into account that when I show a detail view controller when selecting an item in the main one, the split view controller creates another instance of the detail view controller each time. And since I was setting the detail object on the old instance, the old instance was updated but another one was already displayed. All I had to do to fix my issue was to make sure that I always set my detail object on the current instance of the detail view controller.

I hope this is useful to somebody.