oracular (3) Data::Dumper::Simple.3pm.gz
NAME
Data::Dumper::Simple - Easily dump variables with names
SYNOPSIS
use Data::Dumper::Simple;
warn Dumper($scalar, @array, %hash);
warn Dumper($scalar, \@array, \%hash);
warn Dumper $scalar, @array, %hash;
ABSTRACT
This module allow the user to dump variables in a Data::Dumper format.
Unlike the default behavior of Data::Dumper, the variables are named
(instead of $VAR1, $VAR2, etc.) Data::Dumper provides an extended
interface that allows the programmer to name the variables, but this
interface requires a lot of typing and is prone to tyops (sic). This
module fixes that.
DESCRIPTION
"Data::Dumper::Simple" is actually a source filter that replaces all instances of "Dumper($some, @args)"
in your code with a call to "Data::Dumper->Dump()". You can use the one function provided to make
dumping variables for debugging a trivial task.
Note that this is primarily a debugging tool. "Data::Dumper" offers a bit more than that, so don't
expect this module to be more than it is.
Note that if you strongly object to source filters, I've also released Data::Dumper::Names. It does what
this module does by it uses PadWalker instead of a source filter. Unfortunately, it has a few
limitations and is not as powerful as this module. Think of Data::Dumper::Names as a "proof of concept".
The Problem
Frequently, we use "Data::Dumper" to dump out some variables while debugging. When this happens, we
often do this:
use Data::Dumper;
warn Dumper($foo, $bar, $baz);
And we get simple output like:
$VAR1 = 3;
$VAR2 = 2;
$VAR3 = 1;
While this is usually what we want, this can be confusing if we forget which variable corresponds to
which variable printed. To get around this, there is an extended interface to "Data::Dumper":
warn Data::Dumper->Dump(
[$foo, $bar, $baz],
[qw/*foo *bar *baz/]
);
This provides much more useful output.
$foo = 3;
$bar = 2;
$baz = 1;
(There's more control over the output than what I've shown.)
You can even use this to output more complex data structures:
warn Data::Dumper->Dump(
[$foo, \@array],
[qw/*foo *array/]
);
And get something like this:
$foo = 3;
@array = (
8,
'Ovid'
);
Unfortunately, this can involve a lot of annoying typing.
warn Data::Dumper->Dump(
[$foo, \%this, \@array, \%that],
[qw/*foo *that *array *this/]
);
You'll also notice a typo in the second array ref which can cause great confusion while debugging.
The Solution
With "Data::Dumper::Simple" you can do this instead:
use Data::Dumper::Simple.
warn Dumper($scalar, @array, %hash);
Note that there's no need to even take a reference to the variables. The output of the above resembles
this (sample data, of course):
$scalar = 'Ovid';
@array = (
'Data',
'Dumper',
'Simple',
'Rocks!'
);
%hash = (
'it' => 'does',
'I' => 'hope',
'at' => 'least'
);
Taking a reference to an array or hash works as expected, but taking a reference to a scalar is
effectively a no-op (because it can turn into a confusing reference to a reference);
my $foo = { hash => 'ref' };
my @foo = qw/foo bar baz/;
warn Dumper ($foo, \@foo);
Produces:
$foo = {
'hash' => 'ref'
};
$foo = [
'foo',
'bar',
'baz'
];
Note that this means similarly named variables can get quite confusing, as in the example above.
If you already have a &Dumper function, you can specify a different function name with the "as" key in
the import list:
use Data::Dumper::Simple as => 'display';
warn display( $scalar, @array, %hash );
Also, if you really, really can't stand typing "warn" or "print", you can turn on "autowarn":
use Data::Dumper::Simple as => 'display', autowarn => 1;
display($scalar, @array, $some->{ data });
Or you can send the output (as a list) to a different function:
use Data::Dumper::Simple as => 'debug', autowarn => 'to_log';
sub to_log {
my @data = @_;
# some logging function
}
debug(
$customer => @order_nums
); # yeah, we support the fat comma "=>" and newlines
EXPORT
The only thing exported is the Dumper() function.
Well, actually that's not really true. Nothing is exported. However, a source filter is used to
automatically rewrite any apparent calls to "Dumper()" so that it just Does The Right Thing.
SEE ALSO
• Data::Dumper - Stringified perl data structures
• Filter::Simple - Simplified source filtering
BUGS
This module uses a source filter. If you don't like that, don't use this. There are no known bugs but
there probably are some as this is Alpha Code.
LIMITATIONS
• Calling with a sub
Do not try to call "Dumper()" with a subroutine in the argument list:
Dumper($foo, some_sub()); # Bad!
The filter gets confused by the parentheses. Your author was going to fix this but it became
apparent that there was no way that "Dumper()" could figure out how to name the return values from
the subroutines, thus ensuring further breakage. So don't do that.
• Multiple enreferencing
Getting really crazy by using multiple enreferencing will confuse things (e.g., "\\\\\\$foo"), don't
do that, either. I might use "Text::Balanced" at some point to fix this if it's an issue.
• Slices
List and hash slices are not supported at this time.
• String interpolation
"Dumper($foo)" can potentially interpolate if it's in a string. This is because of a weird edge case
with "FILTER_ONLY code" which caused a failure on some items being dumped. I've fixed that, but made
the module a wee bit less robust. This will hopefully be fixed in the next release of
Text::Balanced.
• Line numbers may be wrong
Because this module uses a source filter, line numbers reported from syntax or other errors may be
thrown off a little.
This is probably a bug in the source filter implementation, which should use "#line" directives. As a
workaround until this is fixed, put a directive (such as "#line 10000") a few lines ahead of the
suspected bug. If the error is reported as happening in line 10007, you know to look about eight
lines below your directive for the bug. Be sure to remove the bogus directive once you find the bug!
• The parentheses are optional, but the syntax isn't bulletproof
If you try, it's not hard to confuse the parser. Patches welcome.
Note that this is not a drop-in replacement for "Data::Dumper". If you need the power of that module,
use it.
AUTHOR
Curtis "Ovid" Poe, <eop_divo_sitruc@yahoo.com> Reverse the name to email me.
COPYRIGHT AND LICENSE
Copyright 2004 by Curtis "Ovid" Poe
This library is free software; you can redistribute it and/or modify it under the same terms as Perl
itself.