Has_many etc

I’ve got myself quite mixed up on has_many and related issues.

Suppose I have a lot of Recipes, each of which is to have many
Ingredients.

I think I am meant to do e.g. models/recipe.rb

class Recipe < ActiveRecord::Base
has_many :ingredients
end

along with models/ingredient.rb

class Ingredient < ActiveRecord::Base
belongs_to :recipe
end

Is that right, with the has_many and belongs_to, with the plurality
and use of upper and lower case?

Now I come to my real confusion. I half-think I should create a model
“Recipes_Ingredients”, but I’m not sure on that, so I’ve not done it.

What I have done is to create a table in one of my migrations, viz

class RecipesIngredients < ActiveRecord::Migration
def self.up
create_table :recipes_ingredients, :id => false do |t|
t.column :ingredient_id, :integer
t.column :recipe_id, :integer
end
add_index :recipes_ingredients, [:ingredient_id, :recipe_id]
add_index :recipes_ingredients, :recipe_id
end
def self.down
drop_table :recipes_ingredients
end
end

but is this enough? Am I supposed to use “execute” lines to make up
foreign keys, or will this do what I need?

I think that what I’ve done is insufficient, because no method
recipe.ingredient
seems to have been created. (Hm… is there a way to make the system
describe the methods it’s creating, during migration and otherwise?)

PS. I note that the Roll-With Revisited tutorial http://www.onlamp.com/
pub/a/onlamp/2006/12/14/revisiting-ruby-on-rails-revisited.html?
page=2 illustrates the use of MYSQL code

constraint fk_recipes_categories foreign key (category_id)
references categories(id), primary key(id)

but I’m hoping to avoid hand injection of MySQL. (If I wanted to work
with MySQL directly, I’d be back with PHP!)

Well, I hope I’ve been clear. As readers may guess, I’m not really
working on recipes and ingredients, so I hope I’ve done tthe
conversion to these more evocative names correctly enough that my
point is clear.

PS. I’m using the new RoR, with MySQL.

On 2-Feb-07, at 3:44 PM, dankelley wrote:

end

along with models/ingredient.rb

class Ingredient < ActiveRecord::Base
belongs_to :recipe
end

Is that right, with the has_many and belongs_to, with the plurality
and use of upper and lower case?

this article should get you going Dan - funny enough it’s on subject
too!

http://blog.hasmanythrough.com/2006/3/28/the-other-ways-through

Cheers,
Jodi
General Partner
The nNovation Group inc.
www.nnovation.ca/blog

(Answer to own question.)

I realized that models/ingredients.rb needs

has_and_belongs_to_many :recipes

and that models/recipes.rb needs

has_and_belongs_to_many :ingredients

to get the desired effect.

PS to Jodi – that’s a very informative site you pointed out; thanks
very much.

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