Add a tag function to Rails. Use acts-as-taggable-on


I added the tag function using gem acts-as-taggable-on in Rails. The function I added is a tag function that allows you to prepare existing tags (in the seed file) from new posts and select multiple from them. The image below. スクリーンショット 2020-07-16 22.58.40.png


Ruby 2.5.7 Rails Use design Bootstrap


① Installation


gem 'acts-as-taggable-on', '~> 6.0'


$ bundle install

② Create a table


$ rails acts_as_taggable_on_engine:install:migrations

$ rails db:migrate

③ Added to model and controller


class Style < ApplicationRecord
    acts_as_taggable  #add to

In index, the tag list and what is tagged when the tag is pressed are displayed.


def index
    @tags = ActsAsTaggableOn::Tag.all
    #List of tags
    if params[:tag]
      @styles = Style.tagged_with(params[:tag])
      #When searching for a tag, the one that has the tag removed is displayed.
      @styles = Style.all

def new
    @style =
    @tags = ActsAsTaggableOn::Tag.all

def show
    @style = Style.find(params[:id])

def create
    @style =
    @style.user_id =
      flash[:notice] = "I registered the style"
      redirect_to style_path(
      @tags = ActsAsTaggableOn::Tag.all
      render :new
#Since update and destroy have the same shape, they are omitted.


def style_params
      params.require(:style).permit(:name, :user_id, :image, tag_list: [])
      #  tag_list: []Added


④ Add to seed file This time, we will prepare an existing tag, so use the seed file.


#Tagged tying(%w()Described in)
array = %w(Cute Natural Elegant Mode Women's Mash Men's Mash Short Bob Inner Roll Bob Short Layer Long Layer Layer Women's Perm Men's Perm Men's Cut Men's Two Block Women's Two Block Mohican Men's Business Girls Boys Students Mrs. Balayages Mesh Gradient Color Celebrity Braided Wedding Ceremony Party Casual Makeup Cute Makeup Mode Makeup Natural Makeup Elegant Makeup Adult Ceremony Men's Wolf Women's Wolf Gradient Bob Outer Hane Bob Front Down Sporty Gray Hair Inner Color Earring Color Men's Perm Women's Perm Men's Mesh Men's Color)
array.each{ |tag|
  tag_list = = tag


$ rails db:seed

⑤ Describe in view

<div class="col-xs-12">
   <% @tags.each do |tag| %>
      <%= link_to "#{}(#{tag.taggings_count})", tag_path(, class: "label label-default" %>
   <% end %>
<%= form_for @style do |f| %>
  <div class="col-xs-12">
・ ・ ・ ・ ・ ・ ・
    <label class="col-sm-12">tag</label>
      <div class="col-sm-12">
        <% @tags.each do |tag| %>
          <%= f.check_box :tag_list, { multiple: true }, "#{}", nil %>
          <%= f.label " #{}(#{tag.taggings_count})", class: "label label-default" %>
        <% end %>

      <div class="col-sm-12 text-right">
        <%= f.submit "Create New", class: "btn btn-danger" %>
<% end %>
<label class="col-sm-12 my-top">
   <%= raw( { |t| link_to t, tag_path(t), class: "label label-default" }.join(' ')) %>

The above will look like the following.

The index tagged_with (params [: tag]) narrows down the tags. Click the tag to display the data linked to the tag. In # {}, the tag name is displayed. # {tag.taggings_count} shows the number of registered tags. This completes the implementation.


When deploying to production environment, I got an error with acts-as-taggable-on. If you get an error, please refer to it. I need to modify the tag table,

db/migrate/・ ・ ・_acts_as_taggable_on_migration.acts_as_taggable_on_engine.rb

t.references :tag, foreign_key: { to_table: ActsAsTaggableOn.tags_table }

Despite setting the above foreign key

db/migrate/・ ・ ・ ・_add_missing_unique_indices.acts_as_taggable_on_engine.rb

remove_index ActsAsTaggableOn.taggings_table, :tag_id if index_exists?(ActsAsTaggableOn.taggings_table, :tag_id)

It looks like you're trying to drop the index without dropping the foreign key.

So it worked when I made it like the following.

db/migrate/・ ・ ・ ・_add_missing_unique_indices.acts_as_taggable_on_engine.rb

# This migration comes from acts_as_taggable_on_engine (originally 2)
if ActiveRecord.gem_version >='5.0')
  class AddMissingUniqueIndices < ActiveRecord::Migration[4.2]; end
  class AddMissingUniqueIndices < ActiveRecord::Migration; end
AddMissingUniqueIndices.class_eval do
  def self.up
    add_index ActsAsTaggableOn.tags_table, :name, unique: true

    # remove_index ActsAsTaggableOn.taggings_table, :tag_id if index_exists?(ActsAsTaggableOn.taggings_table, :tag_id)
    #Comment out the above
    if index_exists?(ActsAsTaggableOn.taggings_table, :tag_id) #add to
      remove_foreign_key :taggings, :tags                      #add to
      remove_index ActsAsTaggableOn.taggings_table, :tag_id    #add to
    remove_index ActsAsTaggableOn.taggings_table, name: 'taggings_taggable_context_idx'
    add_index ActsAsTaggableOn.taggings_table,
              [:tag_id, :taggable_id, :taggable_type, :context, :tagger_id, :tagger_type],
              unique: true, name: 'taggings_idx'

  def self.down
    remove_index ActsAsTaggableOn.tags_table, :name

    remove_index ActsAsTaggableOn.taggings_table, name: 'taggings_idx'

    add_index ActsAsTaggableOn.taggings_table, :tag_id unless index_exists?(ActsAsTaggableOn.taggings_table, :tag_id)
    add_index ActsAsTaggableOn.taggings_table, [:taggable_id, :taggable_type, :context], name: 'taggings_taggable_context_idx'

Here, I referred to the following.

In the development environment, I got an error with gem where there was no problem, so I was impatient ... I'm glad if you can use it as a reference.

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