学习Rails - >设置Cookbook应用程序

Question

I'm new to Rails and trying to setup a cookbook app for practice. Here is what I have so far:

DB Setup - 3 tables (simplified for readability)

recipes (id, name, description)

recipe_ingredients (id, recipe_id, ingredient_id, qty, unit)

ingredients(id, name)

Models

class Recipe < ActiveRecord::Base
  has_many :recipe_ingredients, dependent: :destroy
  has_many :ingredients, through: :recipe_ingredients
end

class RecipeIngredient < ActiveRecord::Base
  belongs_to :recipe
  belongs_to :ingredient
end

class Ingredient < ActiveRecord::Base
  has_many :recipe_ingredients
  has_many :recipes, through: :recipe_ingredients
end

Here is my problem. I want to retrieve a list of ingredients for a recipe including qty and the unit used so I can iterate through it in my view.

Here is what I tried (local variables shown, I know I have to use instance variable to use in view) :

recipe = Recipe.first

recipe.ingredients -> gives me all ingredients for that recipe from the ingredients table, but it does not include the qty & unit from recipe_ingredients table.

recipe.recipe_ingredients -> gives me all related records in the recipe_ingredients table but I only get ingredient_id and not the actual ingredient name.

How can I retrieve the recipe and all its ingredients including quantity and unit using the least amount of queries? I think it would be 2 in this case.

Thank you,

Leo

Answer 1

You are looking for the includes method. You need something like this :

recipe = Recipe.includes(:ingredients, :recipeingredients).first

this will return the first recipe with all it's associated ingredients and recipe ingredients.

Answer 2

You can add delegation to increase the functionality of your RecipeIngredient instances.

I would especially check out the prefix section, otherwise you would only be able to delegate name to one class.