members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

messageテーブル

Column	Type	Options
body	text	null: false
image	string	null: true
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
name	string	index: true,null: false

Association

• has_many :users, through: members
• has_many :members
• has_many :messages

usersテーブル

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

Association

• has_many :groups, through: members
• has_many :members
• has_many :messages