What are the pros and cons of using the two different programming styles of CGI.pm with Perl?

Question

I am in a Web Scripting class at school and am working on my first assignment. I tend to overdo things and delve deeper into my subject than what is required in my classes. Right now I am researching CGI.pm to do my HTTP requests and it says there are two programming styles for CGI.pm:

• An object-oriented style
• A function-oriented style

Unless I overlooked the clear answer or am not knowledgeable enough to discern the answer for myself from the documentation provided at: http://perldoc.perl.org/CGI.html I just don't know what the pros and cons are of using these two different styles.

With that being said what are the pros and cons of using the two different styles? Which one is more commonly used? As far as using object-oriented style it says I can only use one CGI object at the time. Why is that?

Thanks for all your help. You have all made studying Computer Science very enjoyable, satisfying, and rewarding for me. =D

Answer 1

Behind the scenes, CGI.pm is doing the same thing despite the styles. The functional interface actually uses a secret object that you don't see.

For many small-scale CGI projects, you're probably never going to need more than one CGI object at a time, so the functional interface is fine. This might be the more common style, but only because most people make small scripts for very specific tasks. If you have a lot of other stuff going on, you might not like CGI.pm importing a long list (and it is long) of function names into your script. Some of the function names might clash with those other modules want to import.

I, however, always use the object-oriented interface. I don't have to worry about name collisions, and it's apparent where any method came from since you see its object. It's also easy to pass the object as arguments to other parts of large applications, etc.

Some people might complain about the extra typing, but that's never been the slow part of programming for me. I've been doing Perl for a long time and I don't mind the syntax. However, I only use CGI to get the input and maybe send the output. I don't mess with any of the HTML stuff.

When it talks about one CGI.pm object at a time, it's referring to access to the input. Once you've read STDIN, for instance, another CGI.pm object won't be able to read that. You can have as many objects as you like though. They just won't share data and the first one gets all of POST data.

You can actually use a mixture though. You can import some things, like :html, but still use the OO interface to deal with the input.

Answer 2

I strongly recommend using the object interface.

Will it be absolutely required for your classwork? No, in fact it is arguably overkill for even small production projects.

However, if you are serious about learning to use CGI.pm for larger scale projects you will need to learn the object method. If you reach the point of needing two objects you will have to use the object interface. Programming, like most everything else, gets better with practice. Practicing now on relatively easier problems will help you be ready for more complex ones.

In fact I'd recommend it as a general rule in programming (although there are exceptions) that if faced with two methods of using a particular tool making a habit of using the one most likely to be used in production code and/or the one that is the correct answer for more of the problem space.