# Method or controller? **URL:** \ **Category:** Rails\ **Created:** [May 25, 2009, 5:59pm UTC](https://www.ruby-forum.com/t/method-or-controller/168774 "2009-05-25T17:59:52Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![byrnejb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/d2c977/32.png) [@byrnejb](https://www.ruby-forum.com/u/byrnejb)\ **Post date:** [May 25, 2009, 5:59pm UTC](https://www.ruby-forum.com/t/method-or-controller/168774/1 "2009-05-25T17:59:52Z")
I wish to allow users to view collections of foreign currency exchange (forex) rates in the following manners: 1. All currencies, only the most current forex rate. and 1. One currency, the N most recent rates. I seem to have several choices here: A. Use the controller for the rates model and use the index method for case 1 and the show method for case 2. B. Use the controller for the rates model and use the index method for case 1 and create a new method, current, for case 2. C. Use two controllers and use the index method in the controller for the rates model (forex\_rates\_controller) to list all currencies and all rates, which is generally the default index behavior; while in the second (current\_forex\_rates\_controller) use index and show as specified in alternative A. Are there any strong preferences for going one way over the other? ---
**Author:** ![byrnejb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/d2c977/32.png) [@byrnejb](https://www.ruby-forum.com/u/byrnejb)\ **Post date:** [May 25, 2009, 6:29pm UTC](https://www.ruby-forum.com/t/method-or-controller/168774/2 "2009-05-25T18:29:58Z")
I am having difficulty understanding the problem, not knowing about forex rates. Could you explain the model structure? I know that controllers do not need to map to models but I think it will help me to understand the structure. Colin 2009/5/25 James B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![byrnejb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/d2c977/32.png) [@byrnejb](https://www.ruby-forum.com/u/byrnejb)\ **Post date:** [May 25, 2009, 7:28pm UTC](https://www.ruby-forum.com/t/method-or-controller/168774/3 "2009-05-25T19:28:01Z")
Colin L. wrote: > I am having difficulty understanding the problem, not knowing about > forex rates. Could you explain the model structure? NP. There is but one model involved. It contains a collection of currency pairs (CAD/USD, CAD/GBP, CAD/JPY, etc.) with specific dates and the exchange rate in effect on that date. So forex.base forex.quote forex.date forex.rate A given pair and date only occurs once in the table (composite unique index). Standard Rails convention has the index action returning all rates for all currency pairs. This is probably not much use in this application. The show action returns a specific rate for a specific pair and date. This is probably useful as is. Users are typically interested in two additional view: The most recent N rates for a specific currency pair; and the rates for all currency pairs on a specific date. ---
**Author:** ![byrnejb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/d2c977/32.png) [@byrnejb](https://www.ruby-forum.com/u/byrnejb)\ **Post date:** [May 25, 2009, 10:59pm UTC](https://www.ruby-forum.com/t/method-or-controller/168774/4 "2009-05-25T22:59:40Z")
Have you considered having a currencies controller? The fact that you talk about currencies suggests that they may the principle resource of interest to the user, even though they do not directly map to a model. The index method would then show all currencies, possibly with a parameter(s) to indicate whether the most recent rates for each currency should be shown, the rates at a particular date, the rate against another particular currency or whatever. The show method would show information for just one currency, again parametrised if necessary. Colin 2009/5/25 James B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)