ruby大神与菜鸟的代码区别

之前Brand类   has_and_belongs_to_many :categories, index: true现在在Category类 增加has_and_belongs_to_many :brands, index: true实现brand.categories关联的数据 同步到 cagegory.brands我写的代码：Brand.each do |brand|  if brand.categories    brand.categories.each do |category|      category.brands << brand      category.save    end  endend 力哥的代码：Category.each do |c|  c.brand_ids = Brand.where(category_ids: c.id).collect(&:id)  c.saveend 大神菜鸟高下立判