Re^4: How to check if an array element reference exists or not

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Re^5: How to check if an array element reference exists or not by almut (Canon) on Apr 14, 2010 at 09:26 UTC
You can use ref to figure out the type of a reference/object. In your case, it seems you don't want to print it if it's "SCALAR"; or maybe the other way round, you do want to print it if it's "HTML::ElementTable::DataElement". `if ( ref($row->[7]) eq "HTML::ElementTable::DataElement" ) { print $row->[7]->as_text; }` [download] Update: a more generic way would be to use can() to directly test whether the method in question is available: `use Scalar::Util 'blessed'; if ( blessed($row->[7]) and $row->[7]->can("as_text") ) { print $row->[7]->as_text; }` [download] `can()` can only be called on blessed references, though, so you'd need to use Scalar::Util... (unless you resort to ugly stuff like `if ("$ref"=~/=/ and ...)` ).	[reply] [d/l] [select]
Re^6: How to check if an array element reference exists or not by corpx (Acolyte) on Apr 14, 2010 at 10:05 UTC
Thanks. That did it!	[reply]
Re^5: How to check if an array element reference exists or not by Corion (Patriarch) on Apr 14, 2010 at 09:23 UTC
The point of using Data::Dumper is to get a textual representation of a data structure, so there is then no need to resort to screenshots of a debugger showing a scrolled window of a data structure. Your debugger is misleading you. You are either not using strict, or you have two variables declared, `@row` and `$row`. They are different. You seem to be wanting to check whether the 8th element in the array referenced by `$row` is defined, but you check whether the 8th element in the array `@row` is defined. Again, use Data::Dumper to look at the data structure you're testing instead of relying on visual inspection combined with guesswork as to what data structure your code really is looking at. `if (defined $row->[7]) { ...` [download] should work, according to my interpretation of the dump you show in the offsite link to a screenshot showing your debugger showing a data structure and some code.	[reply] [d/l] [select]
Re^6: How to check if an array element reference exists or not by corpx (Acolyte) on Apr 14, 2010 at 10:04 UTC
Thanks again for the reply. I'm not using strict as I'm just writing a function to complement code that somebody else has written. I ran the dumper on `$row`and it spit out a 3200KB text file. So instead, I ran the Dumper on `print Dumper ($row->[7]);` and got `$VAR1 = \undef;`. Running `if (defined ($row->[7]) )` when `$row->[7]` is `\undef;` returns true. I'm guessing that the reference is causing this?	[reply] [d/l] [select]
Re^7: How to check if an array element reference exists or not by Anonymous Monk on Apr 14, 2010 at 10:51 UTC
I'm guessing that the reference is causing this? What is this guessing? `$ perl -le"print \undef" SCALAR(0x3d5790) $ perl -le"print defined \undef" 1 $ perl -le"print \1" SCALAR(0x3d8284) $ perl -le"print defined \1" 1` [download]	[reply] [d/l]