Re^3: uninitialized string variable

[jjw92]

Yes, I am reasonably new to Perl, I am using Text::CSV::Slurp. The @ is used because $data is returned as a reference to an array of hashes, so:

@$data[0] -> {"data"}

Returns the first hash inside data, and points to the value associated with the key "data". *unless my understanding is wrong*

[suhailck]

If $data is a reference to an AoH, then the following is sufficient


perl -le '$data=[{ data => 1 },{a => 2, b => 3}];print $$data[0]->{dat
+a}'
1

And if you try the below code, you can see the error u got,


 perl -wle '$data=[{ data => 1 },{a => 2, b => 3}];print $$data[1]->{c
+}'
Use of uninitialized value in print at -e line 1.

see perldsc for details.

[JavaFan]

$ perl -wE '$data = [{"data" => "foo"}]; say @$data[0]->{"data"}'
foo

However, I would write that as

$$data[0]{"data"}

which doesn't use an unneeded arrow, and uses the more usual dereference sigil. (I guess this case isn't caught by "Scalar value @... is better written as $...).

[choroba]

Isn't it the same as $data->[0]{data} I'd use?

[JediWizard]

This is only an opinion, but:

I would rather keep to a single syntax for de-referencing when possible. As with most things in perl, there is more than one way to do it, and different ways have different strengths. In some cases using the @$arrayref; %$hashref; $$scalarref may be better, and in others $arrayref->[0]; $hashref->{key}; may be better. That having been said... @$data[$i]->{key} uses two different syntax's for de-referecing, in the same statement. I'd say that $data->[$i]{key} is much clearer.