使用 Rails has_many 时的错误：通过关联

Question

我的应用包含用户添加到锻炼中的锻炼。用户可以创建练习或选择现有练习。

*** 更新 **** 我根据 Ben 的解决方案添加了一个模型。 尝试将练习添加到锻炼时，我收到如下错误。我的语法错了吗？我尝试过像this这样的解决方案：

w=Workout.last
e=Exercise.last

w.exercises.build(:exercise => e)  # NameError: uninitialized constant Workout::ExercisesWorkout
w.exercises_workouts.create(:exericse_id => 1) #NameError: uninitialized constant Workout::ExercisesWorkout

我对关联中附加的新方法以及是否有“_”、camelCase、Pluralize、symbol..等感到困惑。

Rails 似乎正在寻找 ExercisesWorkout 类，但我定义了“exercises_workouts”和/或ExercisesWorkouts。

谢谢。

---

我在从 rails 控制台向锻炼添加锻炼时遇到问题。我看到的 2 个潜在问题：

1. 我不知道执行此操作的正确语法（构建、创建、查找）
2. 应用程序设置正确（连接表、模型等）

请让我知道我的错误在哪里以及是否有更好的结构/关联可供使用。

谢谢。

型号：

class Exercise < ActiveRecord::Base
    has_many :workouts, :through => :exercises_workouts
    has_many :exercises_workouts
end


class Workout < ActiveRecord::Base
    has_many :exercises, :through => :exercises_workouts
    has_many :exercises_workouts
end

class ExercisesWorkouts < ActiveRecord::Base
    belongs_to :exercise
    belongs_to :workout
end

schema.db：

ActiveRecord::Schema.define(version: 20141129181911) do

  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"

  create_table "exercises", force: true do |t|
    t.string   "name"
    t.string   "description"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "exercises_workouts", id: false, force: true do |t|
    t.integer "exercise_id", null: false
    t.integer "workout_id",  null: false
  end

  create_table "workouts", force: true do |t|
    t.string   "name"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

end

错误：

 w=Workout.new #create new workout
 w.name = 'test' #name workout
 w.save #save workout

 e1=Exercise.new #create new exercise
 e1.name='press' #name exercise
 e1.save #save exercise

#I'm not sure of the syntax here... I've tried alot between create, build using symbols and finds...., this is just one example.. 
 w.exercises.create(e1) #NameError: uninitialized constant Workout::ExercisesWorkout

Answer 1

您还需要一个连接表的模型：

class ExercisesWorkouts < ActiveRecord::Base
    belongs_to :exercise
    belongs_to :workout
end

如果您有兴趣，这里是更详细地涵盖连接表的答案：

What would the joining table called in this case in Rails 3.1?