creating a record with a has many through association - ruby-on-rails

Question

I would like to create an association to another a model when creating a record.
The models use the has_many through association.
Models
Recipe
class Recipe < ApplicationRecord
attribute :name
attribute :published
has_many :ingridients, dependent: :destroy
has_many :instructions, dependent: :destroy
has_many :recipe_seasons
has_many :seasons, through: :recipe_seasons
accepts_nested_attributes_for :recipe_seasons
validates_presence_of :name
end
Season
class Season < ApplicationRecord
has_many :recipe_seasons
has_many :recipes, through: :recipe_seasons
end
RecipeSeason
class RecipeSeason < ApplicationRecord
belongs_to :recipe
belongs_to :season
validates_presence_of :recipe
validates_presence_of :season
accepts_nested_attributes_for :season
end
Controller
def new
#month = 1
#recipe = Recipe.new
#recipe.recipe_seasons.build(season_id: #month).build_recipe
end
def create
#recipe = Recipe.new(recipe_params)
#recipe.save
redirect_to recipes_path
flash[:notice] = I18n.t("recipe.created")
end
private
def recipe_params
params.require(:recipe)
.permit(:name, :published, recipe_seasons_attributes:[:recipe_id, :season_id ])
end
When the Recipe is created, I'd like a defauly value of #month to be inserted into a record on the table recipe_seasons using the id of the newly created Recipe.
Form
<%= form_with(model: #recipe) do |f| %>
<%= f.label :name %>
<%= f.text_field :name, required: true %>
<%= f.label :published %>
<%= f.check_box :published, class: "form-control", placeholder: "Tick if done" %>
<%= f.submit %>
<% end %>
<%=link_to t("back"), recipes_path %>
When I create a recipe, I would like a record to be inserted into recipe_seasons at the same time, using the id that is created on the recipe as the recipe_id on the table recipe_seasons. For now I will hard code a value for #month that is used for the season_id.

Answer 1

You're actually overdoing and overcomplicating it here. You don't need anything in your RecipeSeason class except:
class RecipeSeason < ApplicationRecord
belongs_to :recipe
belongs_to :season
end
The presence validations are added by default to belongs_to assocations since Rails 5. You do not need nested attributes to just assign assocatiated items.
Normally when dealing with join tables you do not need to explicitly create the join models as they are created implicitly through the assocation:
def create
#recipe = Recipe.new(recipe_params)
# Always check if the record was valid and saved
if #recipe.save
redirect_to recipes_path, status: :created
flash[:notice] = I18n.t("recipe.created")
else
render :new
end
end
def recipe_params
params.require(:recipe)
.permit(:name, :published, season_ids: [])
end
<%= form_with(model: :recipe) do |form| %>
<%= form.collection_select(
:season_ids, # name of the attribute
Season.all, # the collection which should be available as options
:id, # value method
:name # label method
) %>
<% end %>
This uses the setter created by has_many :seasons, through: :recipe_seasons and will automatically create/delete rows in the recipe_seasons table.
If you want to create a default you just set the selected attribute on the select element.
<%= form.collection_select :season_ids, #seasons, :id, :name, selected: #seasons.first.id %>
The only time you need to explicitly create the intermediate model is when its not just used as a simple join table and your passing properties for that table. For example if your have an order form and you want to add a product to the order together with a quantity:
# order.products << #product won't let us pass a quantity
order.line_items.create(
product: #product,
quantity: 50
)
That's when nested attributes actually becomes relevant.