Trying create a subclass object from the parent objects controller - ruby-on-rails

Question

I'm trying to figure out how I can grab the current instance of an object called "meal" to create a food object that belongs to it.
It works in console... its simple and goes like this:
user = User.first
user.meal.first.meal_foods.create
A user can have many meals, and each meal can have many meal_foods.
The challenge here for me is in the create action of the foods controller in creating my meals_food.
(I'm using STI here hence the "foods" controller and the "meal_food" name)
Currently the create action looks like this:
#food = current_user.meal.meal_foods.build
I've also tried this because something pluralizing the objects name works
#food = current_user.meal.meal_food.build
Here's the error it gives for both
undefined method `meal_foods' for [#<Meal id: 17, user_id: 1, meal_name: "Meal">]:ActiveRecord::Relation
Update:
The issue I'm having here specifically is selecting the correct meal to create a meal_food for.
In console I can select the first one, which is fine. But in the foods controller, I need to select the correct meal for which to create a meal_food.
Writing meals.first would select the very first meal for that user. If I want to select the 3rd meal out of 5, I need to figure a way to grab that meal's id.
I've just tried this:
<%= link_to "new food", foods_path(id: meal.id), method: :create %>
to pass in the meal.id as a parameter that can be used in foods_controller. And then in the foods_controller I did:
#meal_food = current_user.meals.find_by_id(params[:id]).meal_foods.build
It looks like it's submitting because the page is reloaded with a success message, but the meal_food isn't created, so it just doesn't show up.
I checked in console, and there's no new food being created for this users first meal.
Ok I realized that the link_to I wrote above creates this url:
foods?id=29
and the method I'm using to retrieve this id isn't working because params[:id] is looking for a path id, not this url id.
Thanks in advance!
The Models:
class Meal < ActiveRecord::Base
before_save :sanitize
has_and_belongs_to_many :meal_foods
attr_accessible :meal_name
def sanitize
self.meal_name = "Meal"
end
end
class Food < ActiveRecord::Base
attr_accessible :brand, :carbs, :fat, :name, :protien, :type
end
class MealFood < Food
has_and_belongs_to_many :meals
end
class User < ActiveRecord::Base
has_many :meal, dependent: :destroy
has_many :custom_foods, dependent: :destroy
The controllers:
class FoodsController < ApplicationController
#functions
def create
#this is where I need to grab the correct meal, and then create a meal_food for it...
if #meal_food.save!
flash[:success] = "Food created successfully!"
redirect_to meal_path(current_user.id)
else
flash[:error] = "Food couldn't be created."
redirect_to meal_path(current_user.id)
end
end
end
Partials:
Here's the meal partial that gets repeated to display each meal. It has the link_to for creating a meal that will belong to the meal it's under.
<tr>
<thead class=meal-thead>
<td class=meal-thead-name> <%= meal.meal_name %> </td>
<th> </th>
<th> </th>
<th> </th>
<th> </th>
<th> <%= link_to "x", meal_path(meal.id), method: :delete %> </th>
</thead>
<tbody class=meal-tbody>
<%# get reference to current meal and its foods %>
<%= render meal.meal_foods %>
<td class=remove-td-center> <%= link_to "new food", foods_path, method: :create %> </td>
</tbody>
</tr>

Answer 1

Couple of things:
"has_many :meal, dependent: :destroy" should be "has_many :meals, dependent: :destroy"
has_many association names are pluralized. If you want only one here, use has_one instead.
this line is wrong: #food = current_user.meal.meal_food.build, as meal is a has_many, so you need a "first". Also, it doesn't return a food, but a meal_food, so you should say this, otherwise you are confusing yourself:
#meal_food = current_user.meal.first.meal_food.build
It occurs to me that for MealFood => a better name would be Serving. Then your meal can have_many servings, and each serving can have a food. Not a mistake, just more understandable. Then you'd have the following code. Note that I didn't see the point in the STI for foods - it makes much more sense to simply put the amount of the food eaten in the servings table, then you don't need the STI at all.
class Meal < ActiveRecord::Base
before_save :sanitize
has_many :servings
has_many :foods, :through => :servings
attr_accessible :meal_name
def sanitize
self.meal_name = "Meal"
end
end
class Food < ActiveRecord::Base
attr_accessible :brand, :carbs, :fat, :name, :protein, :type
has_many :servings, :inverse_of => :food
end
class Serving < ActiveRecord::Base
attr_accessible :amount
has_many :foods
has_many :meals
end
class User < ActiveRecord::Base
has_many :meals, dependent: :destroy
end
HTH

Answer 2

Sometimes you say User.meal.meal_foods, sometimes you say User.meal.first.meal_foods. User.meal is an array of Meals, hence from console User.meal.first.meal_foods works, and in your code User.meal.meal_foods gives you no method error. Also, you should use plural meals in your code and swap out has_many meal with has_many meals.