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Alternative Way To Do Global Variables, using __PACKAGE__
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In the process of developing a large website I have found it can be a little onerous at times to use the Request object to pass around global data. I would like to just create variables like $xxx rather than typing $req->{xxx} all the time. It may not seem like much, but after a while your code can start looking a lot more complex because of all the extra brackets and suchlike. As a typical lazy programmer, I looked for a way to simplify this.

The method I am going to describe should be used with caution, because it can increase memory useage rather dramatically if you're not careful. The way I use it, no extra memory is used, but you do need to be aware of the issues.

Basically, you change the way you include files from /base.html, so that they are included into the same package as /base.html:

[- Execute ({inputfile => '*', package => __PACKAGE__}) -]

You should only do this with HTML files which are included from /base.html, not with the files such as subs.html - those files have to be in their own packages in order for Perl inheritance to work. You can't use this technique with any files which are accessed via method calls.

So how does this make things better? Well, since all these files now share the same package, any variables which are created in one of the files is accessible to any of the other files. This means that if you create $xxx in /init.html, then you can access $xxx in /head.html or any other file. This effectively gives you global variables across all the files which are included from /base.html into the same package as /base.html.

The thing you need to be careful of here is that if one of these files is included more than once elsewhere on the website, then it will be seperately compiled for that instance - thus taking up more memory. This is the big caveat. As a rule, if your files are all just included once by /base.html, then you should be fine. Note that you'll also need to change any calls to parent files, for example:

/contact/init.html

[- Execute ({inputfile => '../init.html', package => __PACKAGE__}) -]

[- # Do some setup specific to this subdirectory -]

This is ok, since ../init.html will still be compiled into the same package as the rest of the files included from /base.html, and so only one version of it will exist in the Embperl cache. Thus memory usage is not increased.

I like this technique because it simplifies the look of my code, which is important for projects containing complex algorithms. It is not the "official" way to implement globals though, and should be used with care.


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