How do you populate a collection in a form from a dependent table?

rubyonrails-talk
1

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

2

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

3

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

4

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.