Rails 4- Complex model validation (has_many, through) - ruby-on-rails

Question

I am trying to validate the "name" attribute in my Ingredient model. However, when I add validates :name, :uniqueness => true in my Ingredient model, it does not validate the name (can insert ingredient with same name). The ingredient model has a complex relationship with other model. Please see the code below.
My ultimate goal is to allows user to create ingredient if the ingredient does not exist in the Ingredient table. If the ingredient already existed, used the ingredient id for quantity. If anyone has any idea how to achieve that, please provide the solution to it. Thanks in advance.
ingredient.rb
class Ingredient < ActiveRecord::Base
has_many :quantities
has_many :recipes, through: :quantities
validates :name, :presence => true, :uniqueness => true
end
quantity.rb
class Quantity < ActiveRecord::Base
belongs_to :ingredient
belongs_to :recipe
accepts_nested_attributes_for :ingredient,
:reject_if => :all_blank
validates :ingredient, :uniqueness => true
end
recipe.rb
class Recipe < ActiveRecord::Base
has_many :quantities,
dependent: :destroy
has_many :ingredients,
:through => :quantities
accepts_nested_attributes_for :quantities,
reject_if: :all_blank,
allow_destroy: true
accepts_nested_attributes_for :ingredients
end
view section for creating Ingredient:
%strong Ingredients:
%fieldset#recipe-ingredients
%br
= f.fields_for :quantities do |builder|
= render 'recipe/quantity_fields', f: builder
.links
= link_to_add_association 'add ingredient', f, :quantities, 'data-association-insertion-node' => '#recipe-ingredients', 'data-assoication-insertion-moethod' => "append", :wrap_object => Proc.new{|quantity| quantity.ingredient.build ; quantity}
%br
Ingredient controller:
class IngredientController < ApplicationController
before_action :set_ingredient, only: [:show, :edit, :update, :destroy]
# GET /ingredients
# GET /ingredients.json
def index
#ingredients = Ingredient.all
end
# GET /ingredients/1
# GET /ingredients/1.json
def show
end
# GET /ingredients/new
def new
#ingredient = Ingredient.new
end
# GET /ingredients/1/edit
def edit
end
def create
#ingredient = Ingredient.new(ingredient_params)
respond_to do |format|
if #ingredient.save
format.html { redirect_to #ingredient, notice: 'Ingredient was successfully created.' }
format.json { render :show, status: :created, location: #ingredient }
else
format.html { render :new }
format.json { render json: #ingredient.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /ingredients/1
# PATCH/PUT /ingredients/1.json
def update
respond_to do |format|
if #ingredient.update(ingredient_params)
format.html { redirect_to #ingredient, notice: 'Ingredient was successfully updated.' }
format.json { render :show, status: :ok, location: #ingredient }
else
format.html { render :edit }
format.json { render json: #ingredient.errors, status: :unprocessable_entity }
end
end
end
# DELETE /ingredients/1
# DELETE /ingredients/1.json
def destroy
#ingredient.destroy
respond_to do |format|
format.html { redirect_to ingredients_url, notice: 'Ingredient was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_ingredient
#ingredient = Ingredient.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def ingredient_params
params.require(:ingredient).permit(:name)
end
end

Answer 1

It seems like a known issue probably a bug. Check this: https://github.com/rails/rails/issues/20676