has_one/belongs_to relationship failing.

rubyonrails-talk
1

I have an Ingredient which has a Measurement.

class Ingredient < ActiveRecord::Base   has_one :measurement   belongs_to :recipe

  accepts_nested_attributes_for :measurement end

class Measurement < ActiveRecord::Base   belongs_to :ingredient end

The schemas appear right:

  create_table "ingredients", :force => true do |t|     t.integer "measurement_id"     t.integer "recipe_id"     t.string "quantity"     t.string "food"     t.datetime "created_at"     t.datetime "updated_at"   end

  create_table "measurements", :force => true do |t|     t.string "size"     t.float "quantity"     t.string "abbreviation"     t.string "measurement"     t.string "measurement_type"     t.string "equivalent"     t.datetime "created_at"     t.datetime "updated_at"   end

But I'm still getting this error preventing me from doing an ingredient.measurement.abbreviation, but ingredient.measurement_id works:

ActiveRecord::StatementInvalid in Recipes#show

Showing /Users/mkidd/Sites/cookbook/app/views/recipes/show.html.erb where line #14 raised:

SQLite3::SQLException: no such column: measurements.ingredient_id: SELECT "measurements".* FROM "measurements" WHERE ("measurements".ingredient_id = 1) LIMIT 1

Extracted source (around line #14):

11: <% for ingredient in @recipe.ingredients%> 12: <li> 13: <%= ingredient.quantity %> 14: <%= ingredient.measurement %> 15: <%= ingredient.food %> 16: </li> 17: <% end %>

2

It is the belongs_to object that should have the foreign key, so measurement should have an ingredient_id, not vice versa. Or the relationship should be the other way round.

Colin

3

Colin Law wrote in post #989292:

4

You could have an ingredient_measures table that belongs_to a recipe (recipe has_many ingredient_measures). Each ingredient_measures record specifies an ingredient and a measure of that ingredient for the recipe. So you would also need ingredient_measure belongs_to ingredient and belongs_to measure and ingredient and both ingredient and measure has_many ingredient_measures.

So for a recipe, @recipe, then @recipe.ingredient_measures will give all the ingredients with their measures.

In effect this is a HABTM relationship between ingredient and recipe through ingredient_measures, but there is probably no need to specify it like that unless you need to iterate all ingredients for a particular measure or vice versa, which I guess you probably don't need.

Colin