This isn't a Perl question - this is a general programming question, so you wouldn't have seen it in any Perl-specific book, except in one of those sidebars. That's why places like here exist.

The great Joel Spolsky

The solution he is advocating ... there is an issue with how DAOs (Data Access Objects) are created in Java, JSP, ASP, and .Net applications. The interface is poor, to say the least. Joel is discussing a fix for a specific issue that causes many Windows developers great pain. This is similar to some of the solutions in ANSI C for memory management.

The reason that the solution is poor in the general context has to do with what's known as "Separation of Concerns", more commonly known as "Who cares?". Items in a group should have no knowledge of the fact that they're in a group. The group should know how about the items in it and how to iterate over them. Often, a helper object is created, called an iterator, which can be exposed to the client that allows for syntactic sugar in iteration. (It also allows for more than one iterator to exist at one time.) The point is that the items in the group don't care about the other items in the group. The only entity that cares about that is the group itself. So, it should be the only one that can do anything about group membership.

Put another way - finding the next member is closely linked to adding a new member. Would you ask an item in a group to add another member to said group? I wouldn't.

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We are the carpenters and bricklayers of the Information Age.

Then there are Damian modules.... *sigh* ... that's not about being less-lazy -- that's about being on some really good drugs -- you know, there is no spoon. - flyingmoose

I shouldn't have to say this, but any code, unless otherwise stated, is untested

In reply to Re^3: An object replacing itself by dragonchild
in thread An object replacing itself by ryantate

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