Rails - Aug 2006 - Best way to get data from n+1 models

Hello there.

Sometime ago I asked was the best way to retrieve data like an "union 
all", and unfortunely I could not find the URL on the forum. I asked 
about, for example, hotel rooms and reservation. On another case, I 
could ask for a plane occupation: a model that takes care of the sold 
tickets and another one with the reservations. To get the full map of 
the plane I need to get all the data from both models, on a specific 
date and time. So if I have:

class Ticket extends ActiveRecord::Base
end

class Reservation extends ActiveRecord::Base
end

I could ask for tickets and reservations like

t = Ticket.find(:all,:conditions=>["flight_id=? and 
date=?",flight,date])
r = Reservation.find(:all,:conditions=>["flight_id=? and 
date=?",flight,date])

And get the full map with t.concat(r). That was an answer for my 
previous question and I thank you dudes for that.

My doubt now is what''s the best place to put this stuff. Suppose I want
a FlightMap object, where I can send the flight id and date and get the 
array with the info above. The best way is create a model (with no 
table) to do this, with a method to return the data? Like

class FlightMap
   def map(flight_id,date)
      <code above inserted here>
   end
end

FligthMap.map(flight_id,date)

Is that correct? The file flight_map.rb will be on the models directory, 
creating the FlightMap model, used just to join information of the other 
tables? There is no FligthMap table to join this kind of information, is 
a dynamic operation based on a specific date, retrieving the data from 
the other tables.

I think it works but need some more opinions if this is the correct way 
to do that. ;-)

Thanks!

-- 
Posted via http://www.ruby-forum.com/.

Hi --

On Tue, 8 Aug 2006, Eustáquio Rangel wrote:
> Hello there.
>
> Sometime ago I asked was the best way to retrieve data like an "union
> all", and unfortunely I could not find the URL on the forum. I asked
> about, for example, hotel rooms and reservation. On another case, I
> could ask for a plane occupation: a model that takes care of the sold
> tickets and another one with the reservations. To get the full map of
> the plane I need to get all the data from both models, on a specific
> date and time. So if I have:
>
> class Ticket extends ActiveRecord::Base
> end
>
> class Reservation extends ActiveRecord::Base
> end
>
> I could ask for tickets and reservations like
>
> t = Ticket.find(:all,:conditions=>["flight_id=? and
> date=?",flight,date])
> r = Reservation.find(:all,:conditions=>["flight_id=? and
> date=?",flight,date])
>
> And get the full map with t.concat(r). That was an answer for my
> previous question and I thank you dudes for that.
>
> My doubt now is what''s the best place to put this stuff. Suppose I
want
> a FlightMap object, where I can send the flight id and date and get the
> array with the info above. The best way is create a model (with no
> table) to do this, with a method to return the data? Like
>
> class FlightMap
>   def map(flight_id,date)
>      <code above inserted here>
>   end
> end
>
> FligthMap.map(flight_id,date)
>
> Is that correct? The file flight_map.rb will be on the models directory,
> creating the FlightMap model, used just to join information of the other
> tables? There is no FligthMap table to join this kind of information, is
> a dynamic operation based on a specific date, retrieving the data from
> the other tables.
>
> I think it works but need some more opinions if this is the correct way
> to do that. ;-)
Assuming you have a Flight class and flights table, you could just do
something like:

   class Flight < AR::Base
     has_many :tickets
     has_many :reservations

     def map(date)
       tickets.concat(reservations)
     end
   end

I''m not sure this is the optimal way to model the domain, but I think
it corresponds to what you''re describing.


David

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