Subarray in a hash: Can't use string ("STRING") as a HASH ref while "strict refs" in use

GeoJunkie has asked for the wisdom of the Perl Monks concerning the following question:

I've got a situation where I need to build an array of hashes of arrays of hashes (complex, yes, but it really is needed!) I'm getting a weird error, though. Here's a sampling of code that throws the error:

my @array_of_hashes;

for (my $i=1; $i<=10; $i++) {
    $array_of_hashes[$i] = (
        stuff => 'stuffy',
        goes => 'gooey',
        here => "more $i"
    );

    $array_of_hashes[$i]{sub_data}[6] = "seven";
}
[download]

When I execute this, I get: "Can't use string ("more 1") as a HASH ref while "strict refs" in use" at the last assignment operation ($array_of_hashes$i{sub_data}6 = "seven";). Any ideas why and how I can go about adding a hash with a subarray in this way?

Thanks!

Comment on Subarray in a hash: Can't use string ("STRING") as a HASH ref while "strict refs" in use Download Code

Replies are listed 'Best First'.
Re: Subarray in a hash: Can't use string ("STRING") as a HASH ref while "strict refs" in use by choroba (Cardinal) on Apr 08, 2014 at 13:39 UTC
Round parentheses `( ... )` don't create a reference. Instead, use `{ ... }` to create a hash reference: `my @array_of_hashes; for (my $i=1; $i<=10; $i++) { $array_of_hashes[$i] = { stuff => 'stuffy', goes => 'gooey', here => "more $i" }; $array_of_hashes[$i]{sub_data}[6] = "seven"; }` [download] Update: In your original code, assignment to a hash value introduced a scalar context. In scalar context, the list in parentheses returned its last member, `"more $i"`. You later tried to use this value as a hash reference. لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l] [select]
Re^2: Subarray in a hash: Can't use string ("STRING") as a HASH ref while "strict refs" in use by GeoJunkie (Initiate) on Apr 08, 2014 at 13:48 UTC
That did it! Is this just because it's a hash within an array? Normally, when defining a hash (as %hashname), you use round parentheses - at least that's what the Perl Cookbook says. Thanks!	[reply]
Re^3: Subarray in a hash: Can't use string ("STRING") as a HASH ref while "strict refs" in use by choroba (Cardinal) on Apr 08, 2014 at 13:51 UTC
`( )` are used for assignments to arrays and hashes. `[ ]` are used for array references, `{ }` are used for hash references. You are not assigning a hash, you are assigning a hash reference here. Updated. لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l] [select]
Re^4: Subarray in a hash: Can't use string ("STRING") as a HASH ref while "strict refs" in use by shawnhcorey (Friar) on Apr 08, 2014 at 14:22 UTC
Re^3: Subarray in a hash: Can't use string ("STRING") as a HASH ref while "strict refs" in use by andal (Hermit) on Apr 08, 2014 at 13:52 UTC
Compare `%hash = (key1 => 'val1', key2 => 'val2'); $hash = {key1 => 'val1', key2 => 'val2'};` [download] The first one defines hash, the second defines reference to hash, which is scalar.	[reply] [d/l]
Re: Subarray in a hash: Can't use string ("STRING") as a HASH ref while "strict refs" in use by AnomalousMonk (Archbishop) on Apr 08, 2014 at 17:58 UTC
Had you been using warnings, Perl would have given you some hints that might have been enlightening: c:\@Work\Perl\monks>perl -wMstrict -le "my @array_of_hashes; for (my $i=1; $i<=10; $i++) { $array_of_hashes[$i] = ( stuff => 'stuffy', goes => 'gooey', here => \"more $i\" ); $array_of_hashes[$i]{sub_data}[6] = \"seven\"; } " Useless use of a constant (stuff) in void context at -e line 1. Useless use of a constant (stuffy) in void context at -e line 1. Useless use of a constant (goes) in void context at -e line 1. Useless use of a constant (gooey) in void context at -e line 1. Useless use of a constant (here) in void context at -e line 1. Can't use string ("more 1") as a HASH ref while "strict refs" in use a +t -e line 1. [download]	[reply] [d/l]