undefined method or my Active Record mistakes - ruby-on-rails

Question

Sorry if my problem will be silly but Rails are new to me. I made two models and two controllers. My problems were started after I made second model and added reference to the first one.
class SentencesController < ApplicationController
before_action :find_story
def create
#sentence = find_story.sentences.build(sentence_params)
if #sentence.save
flash[:success] = "You wrote the continuation!"
render 'stories/show'
else
render 'stories/show'
end
end
private
def sentence_params
params.require(:sentence).permit(:content)
end
def find_story
#story = Story.find(params[:id])
end
end
and this:
class StoriesController < ApplicationController
........
def show
#story = Story.find(params[:id])
#sentence = #story.sentences.build
end
.........
end
And I have a problem with defining instance variable #story = Story.find(params[:id]). Error: ActiveRecord::RecordNotFound in SentencesController#create. I have tried many combinations.
This is my migrate files:
class CreateStories < ActiveRecord::Migration[5.1]
def change
create_table :stories do |t|
t.string :title
t.text :content
t.timestamps
end
end
end
class CreateSentences < ActiveRecord::Migration[5.1]
def change
create_table :sentences do |t|
t.text :content
t.references :story, foreign_key: true
t.timestamps
end
add_index :sentences, [:story_id, :created_at]
end
end
What did I do wrong?
EDIT (routes):
Rails.application.routes.draw do
root 'stories#index'
get 'stories/show'
get 'stories/new'
resources :stories
resources :sentences, only: [:create]
end
and schema:
ActiveRecord::Schema.define(version: 20180322121215) do
create_table "sentences", force: :cascade do |t|
t.text "content"
t.integer "story_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["story_id"], name: "index_sentences_on_story_id"
end
create_table "stories", force: :cascade do |t|
t.string "title"
t.text "content"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
end

Answer 1

As stated in the comments, you probably want your routes to look something like:
resources :stories do
resources :sentences, only: [:create]
end
Which will give you:
story_sentences POST /stories/:story_id/sentences(.:format) sentences#create
stories GET /stories(.:format) stories#index
POST /stories(.:format) stories#create
new_story GET /stories/new(.:format) stories#new
edit_story GET /stories/:id/edit(.:format) stories#edit
story GET /stories/:id(.:format) stories#show
PATCH /stories/:id(.:format) stories#update
PUT /stories/:id(.:format) stories#update
DELETE /stories/:id(.:format) stories#destroy
Which you might use something like:
<%= form_tag story_sentences_path(#story) do %>
...
<% end %>
Then, as Matt said, change your find to:
#story = Story.find(params[:story_id])

Answer 2

There are a couple of reasonable ways you can find the story in your sentences controller.
You can add a story_id field to your form and submit it as a param along with the sentence content. Just make sure to add it to sentence_params in the controller so it's not ignored.
def sentence_params
params.require(:sentence).permit(:content, :story_id)
end
And then you'll need to update your find_story method in the controller to:
#story = Story.find(sentence_params[:story_id])
You can set up nested resources in your routes file (where the sentences resource is nested within the stories resource). That will give you access to the story_id from the route itself (ie. you wouldn't need to submit the story_id through the form).
And if you go this way, you'll also need to tweak the find_story method in the controller, but this time it should be:
#story = Story.find(params[:story_id])