[eluser]jedd[/eluser]
[quote author="Nouman6" date="1267583313"]
hmm I was under the impression that checking for a unique entry such as the name was done by the controller during form_validation through callback. Here's how I have it setup.
[/quote]
You're right - that will work well here, by the looks of your code. I just usually get worried about transactional integrity, but it's a pretty straightforward sequence at the moment.
Depending how large your member_model and group_model are going to be, and how keen you are on separating them, and how much interplay exist between the various methods within each .. you could combine them.
Keeping them separate requires managing inter-model communication (a common cause of confusion around here). Previous straw polls suggested files around 500 lines or so were 'about right', but obviously it's hugely dependent on traffic, design preferences, performance expectations, code complexity and so on.
The approach you've described looks like a good hybrid - having the group_model own a couple of tables.
Personally I find the _model suffix on Model names to be cumbersome, so I come up with names that describe the aggregated functionality, or just use near-synonyms. (My Member model manages the dozen or so tables that things like my People controller rely on, f.e.)