usersテーブル

Column	Type	Options
username	string	null: false
email	string	null: false
password	string	null: false

Association

• has_many :messages
• has_many :groups_users
• has_many :groups, through: :groups_users

groups_usersテーブル

Column	Type	Options
user_id	integer	null: false, foreign_key: true
group_id	integer	null: false, foreign_key: true

Association

• belongs_to :user
• belongs_to :group

groupsテーブル

Column	Type	Options
title	text	null: false

Association

• has_many :message
• has_many :groups_users
• has_many :users, through: :groups_users

messagesテーブル

Column	Type	Options
body	text
image	string
user_id	integer	null: false, foreign_key: true
group_id	integer	null: false, foreign_key: true

Association

• belongs_to :user
• belongs_to :group