Question

我有一个对象数组，我需要根据孩子的average_score属性对它们进行排序。我试过sort!，但这似乎不起作用，我不确定我可以在这里使用Rails协会：

collection.sort! do |a, b|
  a.children.where(:user_id => current_user.id).first.average_score <=> b.children.where(:user_id => current_user.id).first.average_score
end

有人可以建议我怎么做吗？

Answer 1

collection.sort_by do |x|
  x.children.where(:user_id => current_user.id).first.average_score
end

虽然我会寻找一种更纯粹，更快速的SQL解决方案。

Answer 2

当a，b是User的实例时，我会这样做

class User
  has_many :children

  # This still looks smelly, has many children
  # but only getting score of first one?
  def children_average_score
    first_child = self.children.where(:user_id => self.id).first

    return first_child.nil ? 0 : first_child.average_score
  end
end

然后排序：

collection.sort! do |a, b|
  a.children_average_score <=> b.children_average_score
end

按子属性对对象数组进行排序

2 个答案: