> -----Original Message-----
> From: John W. Brooking IV [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, December 26, 2001 10:16 AM
> To: [EMAIL PROTECTED]
> Subject: Syntax problems with complex data structure
>
>
> Readers,
>
> I hope you all have had or are having happy holidays of
> your tradition.
>
> I'm trying to build up a complex data structure from a
> file, and cannot
> figure out the right syntax for accessing it afterwards. O'Reilly's
> "Programming Perl" has been very helpful in showing me how to
> build it, but
> I'm having trouble translating from its examples to mine in terms of
> accessing it afterwards, especially after I get it back from
> the function
> that builds it. I suspect my confusion may have something to do with
> references.
>
> My data structure is a hash with two key/value pairs. The
> first value is
> another hash, and the second is an array of hashes. The
> following function
> is an abbreviated sample of the code that builds it. (In the
> real code, I
> read values from a CSV file, but I've left that out of this
> example program
> for the sake of clarity.) I have put some print statements inside the
> function to show that the assignments seem to be working, and
> the syntax
> works fine there. The function returns the plain hash (not a
> reference, but
> maybe it should be?), and the $tableDef{table}{name} syntax
> is working fine
> outside the function, but the $tableDef{colDef}[0]{name}
> syntax only works
> inside the function.
>
> So when I run this code as is, I get (line 48 is the last line)
>
> syntax error at test3.pl line 48, near "print"
> Execution of test3.pl aborted due to compilation errors.
The line above that one is missing the semicolon. Your example
works fine for me if I add the semicolon.
>
> If I comment that line out, I get:
>
> $returnData{colDefs}[0]{name} = "Category"
> $returnData{colDefs}[1]{name} = "Label"
> $returnData{colDefs}[2]{name} = "URL"
> $returnData{colDefs}[3]{name} = "Description"
>
> Table Links: Links to other sites
> Columns (explicitly)
>
> So why does the same syntax that works inside the function not work
> outside it? Should I be returning a reference to the hash
> instead of the
> hash itself? (Which would definately change the syntax
> anyway.) In either
> case, what syntax will work outside the function?
The missing semicolon appears to be the entire problem.
To return a hashref from the sub, you would change
return %returnData;
to
return \%returnData;
Then in the main program, call it like this:
my $tableDef = readfile(); # $tableDef is ref to hash
and access it like this:
print " $tableDef->{colDefs}[0]{name}\n"; # note "->" deref operator
> I would
> like to know how
> to loop through the array using a foreach loop setting the
> loop variable to
> be each hash in the array, as well using a for loop with the
> numeric array
> index as the loop variable or just accessing the array
> elements by literal
> number.
# iterate through list of hashrefs
for my $href (@{$tableDef->{colDefs}}) {
print "$href->{name}\n";
}
# use an index
for my $i (0 .. $#{$tableDef->{colDefs}}) {
print "$tableDef->{colDefs}[$i]{name}\n";
}
>
> In case it makes a difference, I'm using ActiveState Perl
> 5.6.1, binary
> build 626.
>
> Thanks in advance for any advice.
>
> - John Brooking
> Portland, Maine
>
> ------ 8< --- begin code sample --- >8 -----
>
> sub readfile{
> my %returnData;
>
> # Create the table hash element
> $returnData{table} = { name => "Links"
> , desc => "Links to other sites"
> };
>
> # Now create the array of column definitions
> my @fields;
> push @fields, { name => "Category"
> , desc => "Which category of links?"
> , type => "reference"
> , presentation => ""
> };
> push @fields, { name => "Label"
> , desc => "What should this link be called?"
> , type => "character"
> , presentation => "length:25"
> };
> push @fields, { name => "URL"
> , desc => "Web address"
> , type => "character"
> , presentation => "length:50"
> };
> push @fields, { name => "Description"
> , desc => "A short description of this site"
> , type => "character"
> , presentation => "length:2:30"
> };
> $returnData{colDefs} = [@fields];
>
> # Test the values
> print '$returnData{colDefs}[0]{name} = "' .
> "$returnData{colDefs}[0]{name}\"\n";
> print '$returnData{colDefs}[1]{name} = "' .
> "$returnData{colDefs}[1]{name}\"\n";
> print '$returnData{colDefs}[2]{name} = "' .
> "$returnData{colDefs}[2]{name}\"\n";
> print '$returnData{colDefs}[3]{name} = "' .
> "$returnData{colDefs}[3]{name}\"\n";
> print "\n";
>
> # Return the big hash
> return %returnData;
>
> } # sub readfile
>
> my %tableDef = readfile();
> print "Table $tableDef{table}{name}: $tableDef{table}{desc}\n";
> print "Columns (explicitly)\n"
This line is missing a semicolon.
> print " $tableDef{colDefs}[0]{name}\n";
>
>
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