Question

I am trying to implement a many to many relation using a model in rails 3 for my demo app.
It all worked fine untill I tried to add a model that will hold a bit more data on the relation.
I have a recipe, ingredient, Ingredient_Recipe models

File:ingredient_recipe.rb

class IngredientRecipe < ActiveRecord::Base
  attr_accessible :created_at, :ingredient_id, :order, :recipe_id
  belongs_to :recipes
  belongs_to :ingredients
end

File:ingredient.rb

class Ingredient < ActiveRecord::Base
 has_many :ingredientRecipe
 has_many :recipes, :through => :ingredientRecipe
 ...

File:recipes.rb

 class Recipe < ActiveRecord::Base
  has_many :ingredientRecipe
  has_many :ingredients, :through => :ingredientRecipe
  ...

in the ui

 <td >
  <% @recipe.ingredients.each do |ingredient| %>
   ingredient.name
  <% end %>
 </td >

table

 ingredient_id, recipe_id, order, created_at, updated_at

Now, this doesnt work so well…

oh well , and a good resource for implementing many to many would be very apprecieated

Answer 1

I see a few errors in the model code. It is hard to say exactly what those might do.

Your recipes model should look like this:

has_many :ingredient_recipes
has_many :ingredients, :through => :ingredient_recipes

Your ingredient model should look like this

has_many :ingredient_recipes
has_many :recipes, :through => :ingredient_recipes 

Associations should be underscored and lower-cased, has_many relationships should be pluralized.

You said Ingredient_Recipe contains, the content is good but it should be named ingredient_recipe.rb and the class name should be IngredientRecipe unsure if that was just my misunderstanding.

The first error you are experiencing said undefined method recipe_ingredient, which would make sense, the association name is ingredient_recipes, the through parameter takes the exact name of the association.

the second issue is hard to say, but I would make the above modifications first and see if that improves the situation.

the third item, I would say no. Follow the railscast’s instructions.

The railscast in question is a good resource, I have used that specific one before.

EDIT, just noticed the belongs_to is incorrect as well.

within the IncredientRecipe class

belongs_to :recipe
belongs_to :ingredient

a belongs_to association should be singular.