Rails - Mar 2007 - Help moving code into model... get row, modify contents, return to controller

This is probably a total noob question, but I can''t figure it out from
any of my available resources...

I''m trying to move some code into the model.  I want to fetch a row
from the database, modify some of the contents, return the modified
version to the controller, WITHOUT saving the changes to the DB.  The
reason behind this is that I have some status fields in the DB that
equate to words... rather than save strings in the DB, I figured I
would make the columns tinyints, and then change "1" into "Order
pending processing," "2" into "Order entered
production," "3" into
"Production complete, awaiting QC," and so on.

So in my controller I have:

@order = Order.get_formatted_order(params[:id)

and in my model I have:

def self.get_formatted_order(id)
  @order = Order.find(id)
end

This works fine and returns the array to the controller, duh.  But
whenever I try to tinker with the contents, wierd things happen.
First I tried to just replace one element in the array for fun:

def self.get_formatted_order(id)
  @order = Order.find(id)
  @order.status = "In Production"
end

And the odd thing to me is that this only returns "In Production" not
the whole array.  So then I figured I would get smart...

def self.get_formatted_order(id)
  @order = Order.find(id)
  self.status = "In Production"
end

This gets me a "undefined method `status`..."  In desparation I tried
self[:status] and @order[:status] and get variations of the same two
problems.

So how can I pull a row into an array, muss with it, and return the
whole thing to the controller without saving it back to the DB?

Thanks in advance!


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Hey,

comments below:

On 30-Mar-07, at 9:21 PM, andrew.ohnstad-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
wrote:
>
> This is probably a total noob question, but I can''t figure it out
from
> any of my available resources...
>
> I''m trying to move some code into the model.  I want to fetch a
row
> from the database, modify some of the contents, return the modified
> version to the controller, WITHOUT saving the changes to the DB.  The
> reason behind this is that I have some status fields in the DB that
> equate to words... rather than save strings in the DB, I figured I
> would make the columns tinyints, and then change "1" into
"Order
> pending processing," "2" into "Order entered
production," "3" into
> "Production complete, awaiting QC," and so on.
>
> So in my controller I have:
>
> @order = Order.get_formatted_order(params[:id)
>
> and in my model I have:
>
> def self.get_formatted_order(id)
>   @order = Order.find(id)
> end
>
> This works fine and returns the array to the controller, duh.  But
> whenever I try to tinker with the contents, wierd things happen.
> First I tried to just replace one element in the array for fun:
>
> def self.get_formatted_order(id)
>   @order = Order.find(id)
>   @order.status = "In Production"
> end
>
That''s because a ruby method returns the result of your last  
statement - the result there is the value you just assigned to  
@order.status
> And the odd thing to me is that this only returns "In Production"
not
> the whole array.  So then I figured I would get smart...
>
> def self.get_formatted_order(id)
>   @order = Order.find(id)
>   self.status = "In Production"
> end
Same deal - it returns whatever you just assigned to self.status
>
> This gets me a "undefined method `status`..."  In desparation I
tried
> self[:status] and @order[:status] and get variations of the same two
> problems.
>
> So how can I pull a row into an array, muss with it, and return the
> whole thing to the controller without saving it back to the DB?
>
So, the answer to your question is to finish your method with just  
"@order" on it''s own line (or if it makes it clearer for you,
return
@order - but that''s actually a tad slower).

However, I think you''re trying to be too clever by mangling your  
model data just to present human-readable representations of things  
like status fields.  Just write accessors that do the translation:

class Order < ActiveRecord::Base
   ORDER_STATUS_MAP = { 1 => "Pending", 2 =>
"Processing"}

   def status_string
     ORDER_STATUS_MAP[self.status]
   end
end

Then in your views you can do:

Order Status: <%= order.status_string %>

And you don''t have to torture your Order class with stuff like  
"get_formatted_order".

HTH,
Trevor
> Thanks in advance!
>
>
> 
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Trevor,

This is AWESOME!  Thanks a lot for the help.  :)

---A

On Mar 31, 1:37 am, Trevor Squires
<tre...-k8q5a0yEZAgS+FvcfC7Uqw@public.gmane.org>
wrote:
> Hey,
>
> comments below:
>
> On 30-Mar-07, at 9:21 PM,
andrew.ohns...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
>
>
>
>
>
> > This is probably a total noob question, but I can''t figure it
out from
> > any of my available resources...
>
> > I''m trying to move some code into the model.  I want to fetch
a row
> > from the database, modify some of the contents, return the modified
> > version to the controller, WITHOUT saving the changes to the DB.  The
> > reason behind this is that I have some status fields in the DB that
> > equate to words... rather than save strings in the DB, I figured I
> > would make the columns tinyints, and then change "1" into
"Order
> > pending processing," "2" into "Order entered
production," "3" into
> > "Production complete, awaiting QC," and so on.
>
> > So in my controller I have:
>
> > @order = Order.get_formatted_order(params[:id)
>
> > and in my model I have:
>
> > def self.get_formatted_order(id)
> >   @order = Order.find(id)
> > end
>
> > This works fine and returns the array to the controller, duh.  But
> > whenever I try to tinker with the contents, wierd things happen.
> > First I tried to just replace one element in the array for fun:
>
> > def self.get_formatted_order(id)
> >   @order = Order.find(id)
> >   @order.status = "In Production"
> > end
>
> That''s because a ruby method returns the result of your last  
> statement - the result there is the value you just assigned to  
> @order.status
>
> > And the odd thing to me is that this only returns "In
Production" not
> > the whole array.  So then I figured I would get smart...
>
> > def self.get_formatted_order(id)
> >   @order = Order.find(id)
> >   self.status = "In Production"
> > end
>
> Same deal - it returns whatever you just assigned to self.status
>
>
>
> > This gets me a "undefined method `status`..."  In
desparation I tried
> > self[:status] and @order[:status] and get variations of the same two
> > problems.
>
> > So how can I pull a row into an array, muss with it, and return the
> > whole thing to the controller without saving it back to the DB?
>
> So, the answer to your question is to finish your method with just  
> "@order" on it''s own line (or if it makes it clearer for
you, return
> @order - but that''s actually a tad slower).
>
> However, I think you''re trying to be too clever by mangling your  
> model data just to present human-readable representations of things  
> like status fields.  Just write accessors that do the translation:
>
> class Order < ActiveRecord::Base
>    ORDER_STATUS_MAP = { 1 => "Pending", 2 =>
"Processing"}
>
>    def status_string
>      ORDER_STATUS_MAP[self.status]
>    end
> end
>
> Then in your views you can do:
>
> Order Status: <%= order.status_string %>
>
> And you don''t have to torture your Order class with stuff like  
> "get_formatted_order".
>
> HTH,
> Trevor
>
> > Thanks in advance!

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