Re: Require or Do vs. more maintenance

Ultimately the way to do this is to make a library for the start and finish pieces, and make subroutines for them.

package MyAppCommon;
use strict;

sub CommonPageStart {
  ...
}

sub CommonPageEnd {
  ...
}

1;
__END__

# and then, in your scripts
use MyAppCommon;  # use is basically like require... see the docs for 
+details
MyAppCommon::CommonPageStart(...);

# your stuff

MyAppCommon::CommonPageEnd(...);
[download]

This is the "right" way to do it for lots of reasons... not the least of which is that this is the way that most things work, and you will have an easier way of integrating other people's work with yours, as well as having your work be more easily understandable to someone else (if you hire help or if you are asking for help on perlmonks :-D).

As for more direct reasons of why this is better:

It makes your code more easily maintainable and extensible because your code is organized into packages, and it is namespaced (so you can easily add it to another application without worry of namespace collision, and likewise, other modules can be added to it easily without worry of namespace collision)
It is more time-efficient. If you "do" a file, it is read off of disk and parsed with each invocation. However, when a file is "use"d or "require"d (same mechanism, mostly) it is only read off of disk and parsed/compiled once. Further references to it are just referring back to the first copy made. In a mod_perl process, for instance, this can lead to enormous speed improvements.
For much the same reasons, it is more space-efficient. Since the file is only compiled once, the subroutines and data structures and data internal to the perl interpretter (for, say, storing the internal representation of the parsed and compiled code) are only stored once. Again, under mod_perl, this affect can be multiplied even more if your modules are pre-loaded in the parent process (before forking), as each server-process reuses the same copy (more or less) of the compiled code of the modules.
etc

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Re^2: Require or Do vs. more maintenance by Stenyj (Beadle) on Jun 26, 2004 at 20:56 UTC
Alright, that sounds good and makes sense. Question though. I'm hosted on a shared hosting. To make the library, is it just a matter of creating the file with the content you have above, or do I have to do something more specific where I would require higher access to the server (other then FTP)? If I need access to the server (which I can't get) to create a library like you suggested, would 'require' be a equally decent alternative? Thx for all the feedback guys! I always learn a ton when I ask for input here. It's greatly appreciated! Stenyj	[reply]
Re^3: Require or Do vs. more maintenance by etcshadow (Priest) on Jun 26, 2004 at 21:52 UTC
No, you don't need to worry about that. Libraries can live anywhere. You just want to add: `use lib qw( /path/to/my/libraries/ );` [download] At the top of your scripts (or in the initialization file for your web server), to tell perl where to look for libraries. Also, don't let the `use` scare you. It's built on the same mechanism as `require`, basically, there's just some more tricks involved. One consequence of those differences, though, is that you have to use module-names (where the path-separator is "::" and the path is relative to the library path(s)) with a `use` statement, whereas with `require`, you can use either a module-name or a file-name The two things that are different between `use` and `require` are that use happens at BEGIN-time (that is, as the code is being parsed and compiled, rather than later on as the code is being executed). This means, for example, that: `if (0) { use Some::Module; }` [download] will still use the module! use also automatically calls the `import` method of whatever module it is loading, and you can specify parameters to that `import` method after the `use` statement. (Be careful, though, because since the `use` is executed earlier than it looks like in the code, passing variables into the `import` method could cause you hard to understand results... generally just static arguments are passed to the `import` method this way). For example, look up the page at where I said `use lib qw( /path/to/my/libraries/ );`, that actually means that `lib->import( '/path/to/my/libraries/' );` is getting called (lib being a standard core module for manipulating the directory-path). This means that `use Foo::Bar;` is actually equivalent to just: `BEGIN { require Foo::Bar; Foo::Bar->import(); }` [download] Of course, if your module doesn't have an `import` method defined, nothing bad happens, because (since it's a method call, not a function call) it ascends up the class hierarchy to UNIVERSAL::import (...but I'm getting into details, here). Look at ~~`perldoc perlmodlib`~~ `perldoc perlmod` for more info. And good luck! `------------ :Wq Not an editor command: Wq` [download]	[reply] [d/l] [select]
Re^4: Require or Do vs. more maintenance by Stenyj (Beadle) on Jun 26, 2004 at 22:27 UTC
acts like a sponge and absorbs everything Alright, thx! Been trying to get it to work, without luck though. test.cgi `#!c:/apache/perl/bin/perl.exe BEGIN { $\| = 1; open (STDERR, ">&STDOUT"); print qq~Content-type: text/html\n\n~; } use CGI; use strict; use lib qw( c:/apache/cgi-bin/lib ); use MyAppCommon; # use is basically like require... see the docs for my $foo = new CGI; print $foo->header; MyAppCommon::top(); print "Test content (should be in middle)<br><br><br><br>\n"; MyAppCommon::bottom();` [download] MyAppCommon.pl (.pl a necessary extension? or can it be .cgi?) `use strict; sub top { print "Top stuff<br><br>"; } sub test { print "Bottom stuff<br><br>"; } 1;` [download] Assuming the code above, where am I suppose to save MyAppCommon.pl? Does it need to be compiled somehow? I know I could put it in the bin on my test environment, but I want to mimic my website's environment as best possible, so would like to have it in a subdirectory of my cgi-bin. Thx again for all the help, time, and patience! I'm learning a ton tonight :-) Stenyj	[reply] [d/l] [select]
Re^5: Require or Do vs. more maintenance by etcshadow (Priest) on Jun 26, 2004 at 22:45 UTC
Re^5: Require or Do vs. more maintenance by fglock (Vicar) on Jun 26, 2004 at 22:42 UTC