How to make a form to add to join table

Question

I have three tables: recipes, scrapbooks and scrapbook_entries.

My scrapbook_entries is a join table containing (:recipe_id and :scrapbook_id)

The recipe and scrapbook already exist and I am trying to make a form which allows the user to select a scrapbook (from current_user.scrapbooks) and then click 'save' which will take the current recipe (form will be in recipe view) and add the scrapbook_id and recipe_id to the scrabook_entries table.

I already have a scrapbook_entries model and controller. My controller looks like this:

class ScrapbookEntriesController < ApplicationController

def create
    @recipe = current_user.recipes.find(params[:recipe_id])
    @scrapbook = current_user.scrapbooks.find(params[:scrapbook_id])
    @entry = current_user.scrapbook_entries.build(scrapbook: @scrapbook)
    if @entry.save
        flash[:success] = "Added '#{@recipe.name}' to scrapbook '#{@scrapbook.name}'"
    else
        flash[:error] = "Could not add to scrapbook"
    end
    redirect_to @recipe
end

end

My form within the recipe view looks like this:

<%= form_for(@scrapbook_entry, :url => scrapbook_entries_path(params[:id])) do |f| %>
  <%= render 'shared/error_messages', object: f.object %>
    <%= f.number_field :scrapbook_id, placeholder: "Scrapbook ID" %>
    <%= f.hidden_field :recipe_id, :value => @recipe.id %>
  <%= f.submit "Post", class: "btn btn-large btn-primary" %>
<% end %>

As you can see at the moment the user just has to enter the scrapbook_id he/she wants to save it to. I would eventually like to add a list of scrapbooks in a select field but I have had trouble with that so any suggestions would be welcomed!

My form currently renders a "Couldn't find Recipe without an ID" error in the controller once I click submit. Any ideas what I am doing wrong here?

EDIT:

scrapbook.rb

belongs_to :user
has_many :recipes, through: :scrapbook_entries
has_many :scrapbook_entries

recipe.rb

belongs_to :user
has_many :scrapbooks, through: :scrapbook_entries

scrapbook_entry.rb

has_one :recipe
has_one :scrapbook

Answer 1

You're seeing that error because form_for places fields in a nested hash within params. The key for this nested hash is based on the class name of the the model object. Try this:

@recipe = Recipe.find(params[:scrapbook_entry][:recipe_id])

You'll also get an error on the line @entry = current_user.scrapbook_entries ... because User is not directly associated with ScrapbookEntry. Instead, build the entry from the scrapbook:

@entry = @scrapbook.scrapbook_entries.build(recipe: @recipe)

Answer 2

you can try with this

<%=f.select(:scrapbook_id, Scrapbook.all.collect {|p| [ p.id, p.id ] }, {prompt: 'scrapbook'})%>

and if you can create a proper hash so you do not need to assign everything manually. also i can not see the recipe is getting assigned so just pass the whole hash like this

current_user.scrapbook_entries.build(params[:scrapbook_entry])