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Nicholas P. Mueller

2006-Mar-10 03:05 UTC

[Rails] adding to has_many on create and edit

Hello,

I am fairly new to RoR and I have a question I hope can be solved  
elegantly (so many things are, so why not this one too?).  I have a  
working solution, but I want to be sure I am doing things the "rails  
way" (having come from PHP).  You could say I am looking for a little  
validation (no flames please).

I have a table of units like so:

CREATE TABLE `units` (
   `id` int(11) NOT NULL auto_increment,
   `number` varchar(255) NOT NULL default '''',
   `description` text NOT NULL,
   PRIMARY KEY  (`id`)
) TYPE=MyISAM;

that has_many :prices like so:

CREATE TABLE `prices` (
   `id` int(11) NOT NULL auto_increment,
   `price` decimal(10,2) NOT NULL default ''0.00'',
   `unit_id` int(11) default NULL,
   `created_at` datetime NOT NULL default ''0000-00-00
00:00:00'',
   PRIMARY KEY  (`id`),
   KEY `unit_id` (`unit_id`)
) TYPE=MyISAM;

My goal is to be able to create a unit and set its price at the same  
time.  Then, when I update a unit, should I change the price, I want  
to add a new row and time stamp to the price table.

My unit model looks like this:

-----------
class Unit < ActiveRecord::Base
   has_many :prices
   has_one :most_recent_price, :class_name => "Price", :order =>
''created_at DESC''
end
-----------

The has_one :most_recent_price lets me grab the most recent price for  
display and comparison purposes.

I can currently accomplish my aims in the controller like so:

-----------
class AdminUnitsController < ApplicationController
   #snip

   def create
     @unit = Unit.new(params[:unit])
     @unit.prices.create("price" => params[:price])
     @levels = Level.find(:all, :order => "LPAD 
(`levels`.`elevator_number`,5,\"0\") ASC")
     @unit_types = UnitType.find(:all, :order => "`unit_types`.`name`  
ASC")
     if @unit.save
       Unit.find(@unit.id).update_attributes(params[:unit])
       flash[:notice] = ''Unit was successfully created.''
       redirect_to :action => ''list''
     else
       render :action => ''new''
     end
   end

   def update
     @unit = Unit.find(params[:id])
     unless params[:price] == @unit.most_recent_price.price.to_s
       @unit.prices.build("price" => params[:price])
     end
     @levels = Level.find(:all, :order => "LPAD 
(`levels`.`elevator_number`,5,\"0\") ASC")
     @unit_types = UnitType.find(:all, :order => "`unit_types`.`name`  
ASC")
     if @unit.update_attributes(params[:unit])
       flash[:notice] = ''Unit was successfully updated.''
       redirect_to :action => ''show'', :id => @unit
     else
       render :action => ''edit''
     end
   end

   #snip
end
-----------

and a _form.rhtml like so:

-----------
<%= error_messages_for ''unit'' %>

<!--[form:unit]-->
<p><label
for="unit_number">Number</label><br/>
<%= text_field ''unit'', ''number'' 
%></p>

<p><label
for="unit_description">Description</label><br/>
<%= text_area ''unit'', ''description'' 
%></p>

<p><label for="unit_price">Base Price</label><br
/>
$<%= text_field_tag ''price'', @unit.most_recent_price.nil? ?
"0.00" :
@unit.most_recent_price.price %>	
</p>

<!--[eoform:unit]-->
-----------

Is this the "rails way"?  Is there a better way?

Specifically, is the text_field_tag ''price'' construct the best
way to
show/capture the price value or is there a "rails way" of showing/ 
capturing the price value and capturing it with params[] that I don''t  
know about?  If there isn''t, would it be best to move the ternary  
operator statement into the model or is kosher to keep it in the view?

Thanks for any input,

Nick

Francois Beausoleil

2006-Mar-10 03:21 UTC

head link

[Rails] adding to has_many on create and edit

Hi !

2006/3/9, Nicholas P. Mueller
<railsdev@restechservices.net>:> class AdminUnitsController < ApplicationController
>    def create
>      @unit = Unit.new(params[:unit])
>      @unit.prices.create("price" => params[:price])
>      @levels = Level.find(:all, :order => "LPAD
> (`levels`.`elevator_number`,5,\"0\") ASC")
>      @unit_types = UnitType.find(:all, :order =>
"`unit_types`.`name`
> ASC")
>      if @unit.save
>        Unit.find(@unit.id).update_attributes(params[:unit])
>        flash[:notice] = ''Unit was successfully created.''
>        redirect_to :action => ''list''
>      else
>        render :action => ''new''
>      end
>    end
Hmm, this is too complicated.  If you look at your log, you''ll see two
updates to the database:

SQL INSERT - corresponds to "if @unit.save"
SQL UPDATE - corresponds to Unit.find(@unit.id).update_attributes(params[:unit])

You don''t really need the second line - notice you did
Unit.new(params[:unit]) ?  This has the same effect as an
update_attributes to an existing object.
>    def update
>      @unit = Unit.find(params[:id])
>      unless params[:price] == @unit.most_recent_price.price.to_s
>        @unit.prices.build("price" => params[:price])
>      end
>      @levels = Level.find(:all, :order => "LPAD
> (`levels`.`elevator_number`,5,\"0\") ASC")
>      @unit_types = UnitType.find(:all, :order =>
"`unit_types`.`name`
> ASC")
>      if @unit.update_attributes(params[:unit])
>        flash[:notice] = ''Unit was successfully updated.''
>        redirect_to :action => ''show'', :id => @unit
>      else
>        render :action => ''edit''
>      end
>    end
That looks fine.
> Is this the "rails way"?  Is there a better way?
I wouldn''t say there''s a Rails way for this case.  Your
solution is
pragmatic, and it works.  I would have probably done it the same way.

One thing you might want to investigate.  Two times you have this code:
>      @levels = Level.find(:all, :order => "LPAD
> (`levels`.`elevator_number`,5,\"0\") ASC")
>      @unit_types = UnitType.find(:all, :order =>
"`unit_types`.`name`
> ASC")
You should extract that to a filter, like this:

class AdminUnitsController < ApplicationController
  before_filter :load_lookup_data, :except => [:index, :list, :destroy]

  protected
  def load_lookup_data
    @levels = Level.find(:all, :order =>
"LPAD(`levels`.`elevator_number`,5,\"0\") ASC")
    @unit_types = UnitType.find(:all, :order => "`unit_types`.`name`
ASC")
  end
end

Hope that helps !
--
Fran?ois Beausoleil
http://blog.teksol.info/

Nicholas P. Mueller

2006-Mar-10 04:28 UTC

head link

[Rails] adding to has_many on create and edit

Thanks for the advice!

RE: the insert followed by update, that was from some code I had cut/ 
paste from another project.

RE: the filter - I was looking for a way to do something like that!   
Thanks for pointing it out to me!  I''ve written a few projects where  
I was cutting and pasting the same code blocks all over and thought  
there was probably a way to do something, but hadn''t yet bothered to  
look.

Thanks so much,

Nicholas P. Mueller

On Mar 9, 2006, at 9:21 PM, Francois Beausoleil wrote:
> Hi !
>
> 2006/3/9, Nicholas P. Mueller <railsdev@restechservices.net>:
>> class AdminUnitsController < ApplicationController
>>    def create
>>      @unit = Unit.new(params[:unit])
>>      @unit.prices.create("price" => params[:price])
>>      @levels = Level.find(:all, :order => "LPAD
>> (`levels`.`elevator_number`,5,\"0\") ASC")
>>      @unit_types = UnitType.find(:all, :order =>
"`unit_types`.`name`
>> ASC")
>>      if @unit.save
>>        Unit.find(@unit.id).update_attributes(params[:unit])
>>        flash[:notice] = ''Unit was successfully
created.''
>>        redirect_to :action => ''list''
>>      else
>>        render :action => ''new''
>>      end
>>    end
>
> Hmm, this is too complicated.  If you look at your log, you''ll see
two
> updates to the database:
>
> SQL INSERT - corresponds to "if @unit.save"
> SQL UPDATE - corresponds to Unit.find(@unit.id).update_attributes 
> (params[:unit])
>
> You don''t really need the second line - notice you did
> Unit.new(params[:unit]) ?  This has the same effect as an
> update_attributes to an existing object.
>
>>    def update
>>      @unit = Unit.find(params[:id])
>>      unless params[:price] == @unit.most_recent_price.price.to_s
>>        @unit.prices.build("price" => params[:price])
>>      end
>>      @levels = Level.find(:all, :order => "LPAD
>> (`levels`.`elevator_number`,5,\"0\") ASC")
>>      @unit_types = UnitType.find(:all, :order =>
"`unit_types`.`name`
>> ASC")
>>      if @unit.update_attributes(params[:unit])
>>        flash[:notice] = ''Unit was successfully
updated.''
>>        redirect_to :action => ''show'', :id =>
@unit
>>      else
>>        render :action => ''edit''
>>      end
>>    end
>
> That looks fine.
>
>> Is this the "rails way"?  Is there a better way?
>
> I wouldn''t say there''s a Rails way for this case.  Your
solution is
> pragmatic, and it works.  I would have probably done it the same way.
>
> One thing you might want to investigate.  Two times you have this  
> code:
>
>>      @levels = Level.find(:all, :order => "LPAD
>> (`levels`.`elevator_number`,5,\"0\") ASC")
>>      @unit_types = UnitType.find(:all, :order =>
"`unit_types`.`name`
>> ASC")
>
> You should extract that to a filter, like this:
>
> class AdminUnitsController < ApplicationController
>   before_filter :load_lookup_data, :except =>  
> [:index, :list, :destroy]
>
>   protected
>   def load_lookup_data
>     @levels = Level.find(:all, :order =>
> "LPAD(`levels`.`elevator_number`,5,\"0\") ASC")
>     @unit_types = UnitType.find(:all, :order =>  
> "`unit_types`.`name` ASC")
>   end
> end
>
> Hope that helps !
> --
> Fran?ois Beausoleil
> http://blog.teksol.info/
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails

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