Question

This code works at first touch. Preview starts to display (Title, Done, Actions, and blank page) and then previewController:(QLPreviewController *)previewController previewItemAtIndex:(NSInteger)index is called again. This time [self.resultsController objectAtIndexPath:selectedIndexPath]; returns nil – My guess is the entry is no longer selected. index is correct at 1.

The procedure:

- (id)previewController:(QLPreviewController *)previewController previewItemAtIndex:(NSInteger)index
{
    NSIndexPath *selectedIndexPath = [self.tableView indexPathForSelectedRow];
    Manuals *manuals = [self.resultsController objectAtIndexPath:selectedIndexPath];
    NSURL *vUrl = [self locateUrl:[NSURL URLWithString:manuals.Url] ofType:[manuals.Url pathExtension]];    
    return vUrl;
}

If I ignore the exception – the preview continues to display the the document.

I did try to keep the last good returned selectedIndexPath, but then received the error: -[__NSArrayM indexAtPosition:]: unrecognized selector sent to instance 0x1cd52800

The question:

How can I get my resultsController object using only the passed in index?

Answer 1

The problem was in numberOfPreviewItemsInPreviewController:previewController. I was returning the [resultsController count], not the number of documents I wanted to be previewed. When the previewController tried to access the next few objects, it was returning nil.

// Returns the number of items that the preview controller should preview
- (NSInteger)numberOfPreviewItemsInPreviewController:(QLPreviewController *)previewController
{
    return 1;
}