users
create_table :users do |t|
t.timestamps
end
groups
create_table :groups do |t|
t.integer :from_id
t.integer :to_id
t.boolean :is_accept, default: false
end
rails 3.2
User
has_many :groups, class_name: 'Group', foreign_key: :from_id, conditions: 'accept=1'
has_many :group_users, through: :groups, source: :follow_user
Group
belongs_to :user, class_name: 'User', foreign_key: :from_id
belongs_to :follow_user, class_name: 'User', foreign_key: :to_id
rails4
User
has_many :groups, -> { where accept: true }, class_name: 'Group', foreign_key: :from_id
has_many :group_users, through: :groups, source: :follow_user
Group
belongs_to :user, class_name: 'User', foreign_key: :from_id
belongs_to :follow_user, class_name: 'User', foreign_key: :to_id