ruby-on-rails - rails : find_or_create relation

Question

如果我为锻炼创建新练习，我的字段 member_id 为空。

锻炼.rb

     belongs_to :member
     has_and_belongs_to_many :exercises

     def add_exercise_with_name(exercise_name)
        self.exercises << Exercise.find_or_create_by(name: exercise_name)
      end

运动.erb

has_and_belongs_to_many :workouts
belongs_to :member

运动 Controller .erb

def create
    @workout = current_user.workouts.find(params[:workout_id])
    @exercise = @workout.add_exercise_with_name(exercises_params['name'])
    redirect_to workout_path(@workout)
end

如何为练习添加成员？

Answer 1

将 id 作为额外参数传递给该方法。

def add_exercise_with_name(exercise_name, member_id)
  self.exercises << Exercise.find_or_create_by(name: exercise_name, member_id: member_id)
end

这有副作用。现在，find_or_create 调用将在查找练习时考虑 member_id。如果这是不可取的，请使用 create_with(member_id: member_id) .

self.exercises << Exercise.create_with(member_id: member_id).find_or_create_by(name: exercise_name)

此外，您可以使用 block 语法:

  self.exercises << Exercise.find_or_create_by(name: exercise_name) do |exercise|
    exercise.member_id = member_id
  end