# Methods or actions? ask or tell?

**URL:** <https://www.ruby-forum.com/t/methods-or-actions-ask-or-tell/169439>\
**Category:** Rails\
**Created:** [June 3, 2009, 7:10pm UTC](https://www.ruby-forum.com/t/methods-or-actions-ask-or-tell/169439 "2009-06-03T19:10:34Z")\
**Posts on this page:** 1\
**Page:** 1

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**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:** [June 3, 2009, 7:10pm UTC](https://www.ruby-forum.com/t/methods-or-actions-ask-or-tell/169439/1 "2009-06-03T19:10:34Z")

</div>

I have been pondering a routing issue for the past few days. This is an  
area of Rails that I have only recently started to study in any detail.  
So, I would appreciate any information you can give regarding the  
preferred approach to my situation.

In our new application we maintain a collection of foreign currency  
exchange rates. For the moment, these come from a single source.  
However, it is already known that a second source will be used in the  
future.

As with most Rails applications, the exchange rates have a surrogate  
primary key. They also have a unique index on the following columns,  
the real primary key:

:currency\_code\_base, :currency\_code\_quote, :effective\_from, :type

The application requirements given as how I see them in REST style  
routing are:

default currency =\> ‘CAD’  
http verb =\> :get

/forex  
=\> most recent rate for every currency, quoted in default currency,  
sorted by currency code

/forex/yyyy  
=\> all rates for all currencies for given year, quoted in default  
currency, sorted by currency code by date

/forex/yyyy/mm  
=\> all rates for all currencies for given month, quoted in default  
currency, sorted by currency code by date

/forex/yyyy/mm/dd  
=\> rate for every currency effective on given date, quoted in default  
currency, sorted by currency code by date

/forex/XXX  
=\> most recent rate for currency code XXX quoted in default currency

/forex/XXX/yyyy  
=\> rates for currency code XXX for given year, quoted in default  
currency sorted by date

/forex/XXX/yyyy/mm  
=\> rates for currency code XXX for given year, and month quoted in  
default currency sorted by date

/forex/XXX/yyyy/mm/dd  
=\> rates for currency code XXX for given date, quoted in default  
currency sorted by date

/forex/XXX/yyyy/mm/dd?until=yyyy/mm/dd  
=\> rates for currency code XXX between given dates (inclusive), quoted  
in default currency, sorted by date

My question is: how to I handle this in the routing file?

The options that I see open to me are to define custom actions in  
currency\_exchange\_rates\_controller.rb and add a routes.rb entry that  
looks something like this:

…

# see map.resources :forex

map.resources :currency\_exchange\_rates  
…  
map.forex ‘/forex/:currency\_code/:year/:month/:day’,  
:month =\> nil,  
:day =\> nil,  
:type =\> ‘CABK’,  
:controller =\> ‘currency\_exchange\_rates’,  
:action =\> ‘single\_by\_date’,  
:requirements =\> { :currency\_code =\> /[A-Z]{3}/i,  
:year =\> /\d{4}/ }

map.forex ‘/forex/:currency\_code’,  
:type =\> ‘CABK’,  
:controller =\> ‘currency\_exchange\_rates’,  
:action =\> ‘single’,  
:requirements =\> { :currency\_code =\> /[A-Z]{3}/i }

map.forex ‘/forex/:year/:month/:day’,  
:month =\> nil,  
:day =\> nil,  
:type =\> ‘CABK’,  
:controller =\> ‘currency\_exchange\_rates’,  
:action =\> ‘by\_date’,  
:requirements =\> { :currency\_code =\> /[A-Z]{3}/i,  
:year =\> /\d{4}/ }

map.resources :forex,  
:type =\> ‘CABK’,  
:controller =\> ‘currency\_exchange\_rates’,  
:only =\> [:index, :show]  
…

Or, I can change the :action =\> key to another argument key, say :method  
=\>, and then parse the params hash for its value inside the index method  
of the controller. I can see arguments for and against both approaches  
and the only thing that I have to guide me is that the former approach,  
:action =\>, seems to be more in keeping with the spirit of “tell, don’t  
ask” as outlined here:

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In either case, the action/method in the controller is simply going to  
call the same named method in the currency\_exchange\_model, passing the  
params hash as the argument, and return the resulting collection to the  
index view.

Thoughts?