Weird NilObjectException

General
1

So I have this bit of code, where fi is a FolderItem. When it runs, Xojo raises a NilObjectException on the third line.

if fi<>nil then
  if fi.Exists=True then
    if fi.IsReadable=True and f.Length>0 then    '<-------- EXCEPTION OCCURS ON THIS LINE

fi is not nil, it exists, and it’s readable and writeable, it has a path, it isn’t locked, and it isn’t a directory, there are no odd characters in the name, and LastErrorCode=0 - or at least that’s what the debugger says.

Any thoughts on why I’m getting a NilObjectException?!?

Weird, really weird. This is with Xojo 2015r3.

2

[quote=222834:@John McKernon]So I have this bit of code, where fi is a FolderItem. When it runs, Xojo raises a NilObjectException on the third line.

if fi<>nil then
  if fi.Exists=True then
    if fi.IsReadable=True and f.Length>0 then    '<-------- EXCEPTION OCCURS ON THIS LINE

fi is not nil, it exists, and it’s readable and writeable, it has a path, it isn’t locked, and it isn’t a directory, there are no odd characters in the name, and LastErrorCode=0 - or at least that’s what the debugger says.

Any thoughts on why I’m getting a NilObjectException?!?

Weird, really weird. This is with Xojo 2015r3.[/quote]

This isn’t directly related to your problem, but generally you should just open the file and handle failure instead of doing much in the way of pre-flight checks.

3

Really? Virtually every example I’ve seen always checks for nil before doing things with an object, including folder items.

In this case, even if a Try/Catch catches the error, I don’t understand what Xojo thinks something (presumably fi) is nil.

4

except you’re not checking FI in both cases
you have F.length

if fi.IsReadable=True and f.Length>0 then '<-------- EXCEPTION OCCURS ON THIS LINE

FI.isreadable
F.LENGTH

and F might be nil

5

[quote=222848:@John McKernon]Really? Virtually every example I’ve seen always checks for nil before doing things with an object, including folder items.

In this case, even if a Try/Catch catches the error, I don’t understand what Xojo thinks something (presumably fi) is nil.[/quote]

Checking for Nil is much different than doing preflight checks of Exists, IsReadable, and Length.

6

Yikes! How incredibly obvious. I’m glad folks like Norman have better eyes than mine.

Thank you! Now I can sleep…:slight_smile: