Getting EXC_BAD_ACCESS exception when accessing non null variable

Question

As you can see in the linked image, I am getting:

EXC_BAD_ACCESS (code=1, address=0x0)

when accessing outline.numberOfChildren but lldb shows that outline is not nil and that outline.numberOfChildren is 0 (which is exactly what it should be in this case). Why is this happening? Thanks.

link to image: https://i.stack.imgur.com/quzUC.jpg

Code:

 func outlineView(_ outlineView: NSOutlineView, isItemExpandable item: Any) -> Bool { 
  if self.rootOutline != nil {
     if let outline = item as? PDFOutline {
         if outline.numberOfChildren == 0 {  // <- Error here
            return false
          }
         return true
       }
     if self.rootOutline!.numberOfChildren == 0 {
       return false
       }
     return true
    }
  return false
 }

link to Xcode project on github: https://github.com/raphaelreyna/Chapters

You should post the code in the question rather than use a screenshot, that is probably why the question got downvoted. — Peter Ruppert, Mar 08 '19 at 01:23
Is `NSOutline` a typo? I found no documents about it and your git hub says `PDFOutline` at the same place. — Ricky Mo, Mar 08 '19 at 02:24

score 0 · Accepted Answer · answered Mar 08 '19 at 05:00

0

The outline is lazily loaded and can't load if the PDFDocument is released from memory. Solution: keep a strong reference to the PDFDocument.

answered Mar 08 '19 at 05:00

Willeke

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But isn't `if let outline = item as? PDFOutline` creating the strong reference you mention? – Cristik Mar 08 '19 at 05:05
This worked, thanks Willeke. I never would have guessed that this was the issue. – rareyna Mar 08 '19 at 06:02
@Cristik `item` is a strong reference to a `PDFOutline` but the `PDFOutline` items don't keep a strong reference to the document, `document` is a weak property of `PDFOutline`. `outlineRoot` is a strong property of `PDFDocument`. Creating a strong reference in `outlineView(_:isItemExpandable:)` wouldn't work because the document is already released. – Willeke Mar 08 '19 at 11:34

Getting EXC_BAD_ACCESS exception when accessing non null variable

1 Answers1