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


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| %>
    <b>Time</b><br />
    <%= f.datetime_select :time %>

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

    <%= f.submit "Create" %>
<% 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



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

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

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?)

then the models would look something like

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

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

  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

You have to rethink your models. At the very least, you need a many to
many relation between foods and meals.

has_and_belongs_to_many :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

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.