Initialized rails-erd gem to generate an ERD schema based on rails models

Gemfile

@@ -34,6 +34,8 @@ group :development do
   gem 'listen', '~> 3.3'
   # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
   gem 'spring'
+  # Generate erd (UML) schema from rails models
+  gem 'rails-erd'
 end
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem

Gemfile.lock

@@ -66,6 +66,7 @@ GEM
       msgpack (~> 1.0)
     builder (3.2.4)
     byebug (11.1.3)
+    choice (0.2.0)
     concurrent-ruby (1.1.8)
     crass (1.0.6)
     erubi (1.10.0)
@@ -119,6 +120,11 @@ GEM
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
+    rails-erd (1.6.1)
+      activerecord (>= 4.2)
+      activesupport (>= 4.2)
+      choice (~> 0.2.0)
+      ruby-graphviz (~> 1.2)
     rails-html-sanitizer (1.3.0)
       loofah (~> 2.3)
     railties (6.1.3.1)
@@ -131,6 +137,9 @@ GEM
     rb-fsevent (0.10.4)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
+    rexml (3.2.5)
+    ruby-graphviz (1.2.5)
+      rexml
     spring (2.1.1)
     sprockets (4.0.2)
       concurrent-ruby (~> 1.0)
@@ -163,6 +172,7 @@ DEPENDENCIES
   listen (~> 3.3)
   puma (~> 5.0)
   rails (~> 6.1.3, >= 6.1.3.1)
+  rails-erd
   spring
   sqlite3 (~> 1.4)
   table_print (~> 1.5)

app/models/activity.rb

@@ -1,8 +1,8 @@
 class Activity < ApplicationRecord
   belongs_to :author, class_name: "User"
   
-  has_one :joined_user_activities
-  has_one :user, :through => :joined_user_activities
+  has_one :joined_user_activity
+  has_one :user, :through => :joined_user_activity
 
   validates :name, presence: true
   validates :author, presence: true