Rails - Apr 2008 - How do you populate a collection in a form from a dependent table?

Hi,

I''m working on a food program.  The user defines foods, enters their
calories, etc.  Then the user goes into a day view with defines a meal
by selected the foods from a drop down list.

So I have a foods controller, a meals controller.

I have the meals model defined with has_many :foods

And I have the foods controller defined with belongs_to :meal

But when I''m not sure when I create the form for it:

<h1>New meal</h1>

<%= error_messages_for :meal %>

<% form_for(@meal) do |f| %>
  <p>
    <b>Time</b><br />
    <%= f.datetime_select :time %>
  </p>

  <p>
    <b>Food</b><br />
    <%= f.text_select :food %>
  </p>

  <p>
    <%= f.submit "Create" %>
  </p>
<% end %>

<%= link_to ''Back'', meals_path %>

The issue is I need f.text_select and the options available to the
user to come from the food table.  Anybody know how that would look in
code?

Thanks,

Ron
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I assume you meant meals has_many :foods and food belongs_to :meal in 
the models...

What you need is some type of relation table inbetween those two, since 
an individual food could appear in any number of meals, could it not?

A simple has_and_belongs_to_many relationship would require a 
foods_meals table like:

def self.up
  create_table :foods_meals, :id => false do
    t.column :food_id, :integer
    t.column :meal_id, :integer
  end
end

with a has_and_belongs_to_many :foods in the meal model, and the 
converse in the  food model. Check the rails wiki for examples of HABTM 
usage.

Another alternative is a full join table, I dunno, like
''servings''.
def self.up
  create_table :servings do
    t.column :food_id, :integer
    t.column :meal_id, :integer
    * whatever other columns you''d like to track, ounces
(aren''t all
those calories per serving size?)
  end
end

then the models would look something like

meal
  has_many :servings
  has_many :foods, :through => :servings

food
  has_many :servings
  has_many :meals, :through => :servings

serving
  belongs_to :meal
  belongs_to :food

At the risk of writing a dissertation on the subject, google for "rails 
has_many through" for a plethora of info and how-to''s
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You have to rethink your models. At the very least, you need a many to
many relation between foods and meals.

Food
has_and_belongs_to_many :meals

Meals
has_and_belongs_to_many :foods

that will allow you to select the same foods for multiple meals.

for a controller and view for that, you might want to check

http://wiki.rubyonrails.org/rails/pages/CheckboxHABTM




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You will probably need some a prototype helper like observe_field to
see what you selected in terms of a meal and update the options for
the foods selection.


On Apr 27, 11:03 pm, alberto
<buildoutmana...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> You have to rethink your models. At the very least, you need a many to
> many relation between foods and meals.
>
> Food
> has_and_belongs_to_many :meals
>
> Meals
> has_and_belongs_to_many :foods
>
> that will allow you to select the same foods for multiple meals.
>
> for a controller and view for that, you might want to check
>
> http://wiki.rubyonrails.org/rails/pages/CheckboxHABTM
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