Rails has_many关联更改为父模型不会反映出来吗？

Question

For example, i have this:

class Family < ActiveRecord::Base
  :has_many :members

  def aging(date)
    members.find_all_by_birthday(date).each do |m|
      m.age = m.age+1
      # i dont want to put a m.save here
    end
  end

  # some validations
end

@family = Family.first
@family.aging("2012-01-04")
@family.members.each do |m|
  puts m.age
end
# it still the old age

I would like to use @family.save after calling aging method but it seems to not work that way, i would like to save this only if all validations met. This is just an example to simplify what i need

Answer 1

The members.find_all_by_birthday(date) does a separate query to return you a collection of members rather than fetching all members for the family into the association and then reducing it to the ones that have the corresponding birthday.

You can do:

members.select { |m| m.birthday == date }.each do |m|
  m.age = m.age + 1
end

Which will modify the members in place. It has the disadvantage of fetching them all from the database which the find_all_by_birthday doesn't as it just fetches the ones you want.