Question

I have this Perl script with many defined constants of configuration files. For example:

use constant  { LOG_DIR                             => "/var/log/", LOG_FILENAME                        => "/var/log/file1.log", LOG4PERL_CONF_FILE                  => "/etc/app1/log4perl.conf", CONF_FILE1                          => "/etc/app1/config1.xml", CONF_FILE2                          => "/etc/app1/config2.xml", CONF_FILE3                          => "/etc/app1/config3.xml", CONF_FILE4                          => "/etc/app1/config4.xml", CONF_FILE5                          => "/etc/app1/config5.xml", }; 

I want to reduce duplication of "/etc/app1" and "/var/log" , but using variables does not work. Also using previously defined constants does not work in the same "use constant block". For example:

use constant { LOG_DIR                             => "/var/log/", FILE_FILENAME                       => LOG_DIR . "file1.log"  }; 

does not work.

Using separate "use constant" blocks does workaround this problem, but that adds a lot of unneeded code.

What is the correct way to do this?

Answer 1

I’d probably write it like this:

use Readonly;  Readonly my $LOG_DIR            => '/var/log'; Readonly my $LOG_FILENAME       => '$LOG_DIR/file1.log'; Readonly my $ETC                => '/etc/app1'; Readonly my $LOG4PERL_CONF_FILE => '$ETC/log4perl.con';  # hash because we don't have an index '0' Readonly my %CONF_FILES => map { $_ => '$ETC/config$_.xml' } 1 .. 5; 

However, that’s still a lot of code, but it does remove the duplication and that’s a win.

Why are your logfiles numeric? If they start with 0, an array is a better choice than a hash. If they’re named, they’re more descriptive.