Add micropost/tag association

app/models/micropost.rb

@@ -7,4 +7,7 @@ class Micropost < ApplicationRecord
   validates :user,
             :content,
             presence: true
+
+  has_many :microposts_tags
+  has_many :tags, through: :microposts_tags
 end

app/models/microposts_tag.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+class MicropostsTag < ApplicationRecord
+  belongs_to :micropost
+  belongs_to :tag
+end

app/models/tag.rb

@@ -2,4 +2,6 @@
 
 class Tag < ApplicationRecord
   validates :name, presence: true
+  has_many :microposts_tags
+  has_many :microposts, through: :microposts_tags
 end

db/migrate/20231019172703_create_join_table_tags_microposts.rb

@@ -0,0 +1,8 @@
+class CreateJoinTableTagsMicroposts < ActiveRecord::Migration[7.1]
+  def change
+    create_join_table :tags, :microposts, primary_key: [:tag_id, :micropost_id] do |t|
+      t.index [:tag_id, :micropost_id]
+      t.index [:micropost_id, :tag_id]
+    end
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2023_10_19_164620) do
+ActiveRecord::Schema[7.1].define(version: 2023_10_19_172703) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -70,6 +70,13 @@ ActiveRecord::Schema[7.1].define(version: 2023_10_19_164620) do
     t.index ["user_id"], name: "index_microposts_on_user_id"
   end
 
+  create_table "microposts_tags", id: false, force: :cascade do |t|
+    t.bigint "tag_id", null: false
+    t.bigint "micropost_id", null: false
+    t.index ["micropost_id", "tag_id"], name: "index_microposts_tags_on_micropost_id_and_tag_id"
+    t.index ["tag_id", "micropost_id"], name: "index_microposts_tags_on_tag_id_and_micropost_id"
+  end
+
   create_table "tags", force: :cascade do |t|
     t.string "name", null: false
     t.datetime "created_at", null: false