Quickly changing a function under test in Test::More

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

Monks,

I'm used to call functions like this:

my %commands =
  (
   command1 => {
         description => "Does something",
         function => sub { my $var = shift; print "var = $var\n"}
        },
 )

my $cmd = 'command1';
$commands{$cmd}{function}($param)
[download]

So I thought it could be as easy to quickly change, for development purposes, a function under test by doing:

my $func = \&version1;
is($func($param), 0, 'makes sense');

my $func = \&version2;
is($func($param), 0, 'does it ?');

sub version1{[some code]}

sub version2{[some code]}
[download]

But no dice. Syntax error.

So how are 'function pointers' used with scalars ?

Thanks !

Comment on Quickly changing a function under test in Test::More Select or Download Code

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Re: Quickly changing a function under test in Test::More by duff (Parson) on Mar 09, 2006 at 13:30 UTC
`my $function = sub { print "hi there @_\n" }; $function->("carcassonne");` [download] See perlreftut and perlref duff	[reply] [d/l]
Re: Quickly changing a function under test in Test::More by fizbin (Chaplain) on Mar 09, 2006 at 14:52 UTC
Others have already pointed you at the appropriate references (which you should now go read), but the basic reason is that this: `$commands{$cmd}{function}($param)` [download] is really (for some values of "really") this: `$commands{$cmd}->{function}->($param)` [download] It's just that perl allows you to omit the `->` bit when you have two adjacent sets of parentheses, braces, or brackets. This phenomenon can be seen be using `Deparse`: `$ perl -MO=Deparse -e 'print $a{funclist}[0](4);' print $a{'funclist'}[0](4); -e syntax OK $ perl -MO=Deparse -e 'print $a{funclist}->[0]->(4);' print $a{'funclist'}[0](4); -e syntax OK` [download] See how the output code is the identical? That means that the input code was parsed identically. (or that you've stumbled onto one of the obscure bugs in `Deparse`) However, in you test code you don't have two adjacent sets of delimiters, so you aren't allowed to omit the `->` bit. Use `$func->($param)`, as other posters have already said. -- `@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/; map{y/X_/\n /;print}map{pop@$_}@/for@/` [download]	[reply] [d/l] [select]
Re: Quickly changing a function under test in Test::More by gube (Parson) on Mar 09, 2006 at 14:18 UTC
Hi try this, `#!/usr/local/bin/perl use strict; use warnings; use Data::Dumper; my %commands = ( 'command1' => { 'description' => "Does something", 'function' => sub { my $var = shift; return "var = $var\n" } } ); my $cmd = 'command1'; print $commands{$cmd}{'function'}->("hello");` [download] It's reference part, to learn more about reference, go through perlref link, above given by duff.	[reply] [d/l]