テーブル設計

userテーブル

Column	Type	Options
id	integer	null: false unique: true
name	string	null: false
email	string	null: false, unique: true

Association

• has_many :groups_users
• has_many :groups, through: :groups_users
• has_many :posts

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 :group
• belongs_to :user

groupテーブル

Column	Type	Options
id	integer	null: false, unique: true
name	string	null: false

Association

• has_many :groups_users
• has_many :users, through: :groups_users
• has_many :posts

postテーブル

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

Association

• belongs_to :user
• belongs_to :group