belongs_to :user has_many :stars, :dependent => :destroy has_many :stared_users, :through => :stars, :source => :user # user -> post の関係を複数作る場合、別の名前(:stared_users)を付け、sourceオプションで本当の名前を指定するらしい。 has_many :posts, :dependent => :destroy has_many :stars, :dependent => :destroy has_many :stared_posts, :through => :stars, :source => :post def starable_for?(post) post && post.user != self && !stars.exist
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