M:N relation error in Rails - ruby-on-rails

Question

i got some error when trying to make relation between Post and Hashtag by m : n
all things fine but when try to save log prints like this
Started POST "/posts" for 127.0.0.1 at 2018-03-05 21:43:00 +0900
Processing by PostsController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"DxRb+4PAfOsDTCEMx+BcBNKK/LWAH5NxwVh6n7OChtwBL/svUQVEBj7mrWdCYB2BIUHO/Gql9UC6mKLMMoPqEg==", "post"=>{"title"=>"please", "content"=>"please!!!!!", "hashtags_attributes"=>{"0"=>{"title"=>"hash1"}, "1"=>{"title"=>"hash2"}, "2"=>{"title"=>"hash3"}}}, "commit"=>"Create Post"}
Unpermitted parameter: hashtags_attributes
Unpermitted parameters: title, content
Hashtag Load (0.2ms) SELECT "hashtags".* FROM "hashtags" WHERE "hashtags"."title" = ? LIMIT ? [["title", "hash1"], ["LIMIT", 1]]
Unpermitted parameters: title, content
Hashtag Load (0.1ms) SELECT "hashtags".* FROM "hashtags" WHERE "hashtags"."title" = ? LIMIT ? [["title", "hash2"], ["LIMIT", 1]]
Unpermitted parameters: title, content
Hashtag Load (0.1ms) SELECT "hashtags".* FROM "hashtags" WHERE "hashtags"."title" = ? LIMIT ? [["title", "hash3"], ["LIMIT", 1]]
(0.0ms) begin transaction
SQL (0.3ms) INSERT INTO "posts" ("title", "content", "created_at", "updated_at") VALUES (?, ?, ?, ?) [["title", "please"], ["content", "please!!!!!"], ["created_at", "2018-03-05 12:43:00.937624"], ["updated_at", "2018-03-05 12:43:00.937624"]]
SQL (0.1ms) INSERT INTO "hashtags_posts" ("hashtag_id", "post_id") VALUES (?, ?) [["hashtag_id", 1], ["post_id", 2]]
(0.3ms) rollback transaction
Completed 500 Internal Server Error in 12ms (ActiveRecord: 1.4ms)
ActiveModel::MissingAttributeError (can't write unknown attribute `id`):
app/controllers/posts_controller.rb:36:in `block in create'
app/controllers/posts_controller.rb:35:in `create'
Rendering /usr/local/var/rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout
Rendering /usr/local/var/rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_source.html.erb
Rendered /usr/local/var/rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_source.html.erb (7.4ms)
Rendering /usr/local/var/rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb
Rendered /usr/local/var/rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (2.0ms)
Rendering /usr/local/var/rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb
Rendered /usr/local/var/rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (1.1ms)
Rendered /usr/local/var/rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout (124.9ms)
i don't know why title content, and hashtags_attributes are unpermitted parameters. i set them in white list correctly
this is my codes
posts_controller.rb
def create
#post = Post.new(post_params)
3.times do |x|
tag = hashtag_params[:hashtags_attributes]["#{x}"]["title"]
a = Hashtag.find_or_create_by(title: tag)
#post.hashtags << a
end
respond_to do |format|
if #post.save
format.html { redirect_to #post, notice: 'Post was successfully created.' }
format.json { render :show, status: :created, location: #post }
else
format.html { render :new }
format.json { render json: #post.errors, status: :unprocessable_entity }
end
end
end
def hashtag_params
params.require(:post).permit(hashtags_attributes: [:title])
end
this is my post.rb
class Post < ApplicationRecord
has_and_belongs_to_many :hashtags
accepts_nested_attributes_for :hashtags
end
this is my hashtag.rb
class Hashtag < ApplicationRecord
has_and_belongs_to_many :posts
end
At last, my _form.html.erb
<%= form_for(post) do |f| %>
<% if post.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(post.errors.count, "error") %> prohibited this post from being saved:</h2>
<ul>
<% post.errors.full_messages.each do |message| %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= f.label :title %>
<%= f.text_field :title %>
</div>
<div class="field">
<%= f.label :content %>
<%= f.text_area :content %>
</div>
<div class="field">
<%= f.fields_for :hashtags do |h|%>
<%=h.label :title, "해시태그"%>
<%=h.text_field :title%>
<% end %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>

Answer 1

You only need to specify post_params correctly:
def create
#post = Post.new(post_params)
respond_to do |format|
if #post.save
format.html { redirect_to #post, notice: 'Post was successfully created.' }
format.json { render :show, status: :created, location: #post }
else
format.html { render :new }
format.json { render json: #post.errors, status: :unprocessable_entity }
end
end
end
def post_params
params.require(:post).permit(:title, :content, hashtags_attributes: [:id, :title])
end
You can read more here
And you need to change your migration
class CreateJoinTableHashtagsPosts < ActiveRecord::Migration[5.0]
def change
create_join_table :hashtags, :posts do |t|
t.index :hashtag_id
t.index :post_id
end
end
end
After it you need to run rake db:rollback && rake db:migrate.
Or you can use rake db:drop && rake db:create && rake db:migrate to recreate db from scratch, in this case you lose all existing data