usersテーブル

Column	Type	Options
name	string	null: false, index: true

Association

• has_many messages

• has_many members

• has_many groups, through :members

membersテーブル

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

Association

• belongs_to group

• belongs_to user

groupsテーブル

Column	Type	Options
name	string	null: false

Association

• has_many members

• has_many messages

• has_many users, through: members

messagesテーブル

Column	Type	Options
text	text
image	text
created_at	timestamp	null: false
user_id	references	null: false, foreign_key: true
group_id	references	null: false, foreign_key: true

Association

• belongs_to user

• belongs_to group