我想在祖父母展示页面下显示孙子记录...我在做什么错？

Question

在我的代码中，用户有学生，学生有日记，日记有diary_entries。我想在学生显示页面下显示每个学生的日记条目。下面是我的模型。

Student.rb模型

class Student < ApplicationRecord
  belongs_to :user
  has_many :diaries, dependent: :destroy
  has_many :teams, dependent: :destroy
  has_many :subjects, dependent: :destroy
  belongs_to :grade

  accepts_nested_attributes_for :diaries
  accepts_nested_attributes_for :subjects
  accepts_nested_attributes_for :teams
end

Diary.rb模型

class Diary < ApplicationRecord
    belongs_to :student
    belongs_to :user
    belongs_to :grade
    has_many :diary_entries

    validates :diary_year, presence: true

    def self.from_student(owner, student_obj)
        new(
            user_id: owner.id,
            student_id: student_obj.id,
            grade_id: student_obj.grade_id,
            diary_year: Date.today.year
        )
    end

end

Diary_entry.rb模型

class DiaryEntry < ApplicationRecord
  belongs_to :diary
  belongs_to :subject
  belongs_to :user

  validates :lesson_date, :assignment, :assignment_due_date, :notes_to_parents, presence: true
end

日记控制器

class DiariesController < ApplicationController
  before_action :authenticate_user!
  before_action :set_student

  def create
    @diary = Diary.from_student(current_user, @student)
    @diary.save
    redirect_to @student, notice: "Diary was successfully created."

  end

  private

  def set_student
    @student = Student.find(params[:student_id])
  end
end

学生控制器#show

 def show
    @diary = @student.diaries
    @diary_entries = @diary.diary_entries
  end

Diary_entries控制器#index和Show

  def index
    @diary_entries = @diary.diary_entries.all
  end

  def show
    @diary_entry = DiaryEntry.find(params[:id])
  end

我希望每个学生每年只有一本日记，所以我在每个日记中添加了一个diary_year列，然后在日记表中添加了student_id和year的唯一索引。

  create_table "diaries", force: :cascade do |t|
    t.bigint "user_id"
    t.bigint "student_id"
    t.bigint "grade_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer "diary_year"
    t.index ["grade_id"], name: "index_diaries_on_grade_id"
    t.index ["student_id", "diary_year"], name: "index_diaries_on_student_id_and_diary_year", unique: true
    t.index ["student_id"], name: "index_diaries_on_student_id"
    t.index ["user_id"], name: "index_diaries_on_user_id"
  end

以下是我在学生显示页面中尝试的循环。

<div class="card">
   <div class="card-body">

     <% @diary_entries.each do |entry| %>
       <li><%= entry.assignment %></li>
     <% end %>
   </div>
 </div>

我希望能够1.让每个学生每年只有一本日记，2.在每个学生页面下显示diary_entries。

Answer 1

您想显示diary_entries的Student，请使用joins

@diary_entries = DiaryEntry.joins(diary: :student)
                           .where(students: { id: @student.id })

有关加入的更多信息-https://guides.rubyonrails.org/active_record_querying.html#joins

尝试一下！

Answer 2

1. 让每个学生每年只有一本日记，

要每年强制执行一个Diary对象，可以在Diary模型中添加一个before_validation。参见Callbacks

回调应调用一个私有函数，该函数检查可能冲突的现有记录。

def ensure_valid_year
  return unless student.diaries.where(diary_year: diary_year).any?
  # code or function call here to handle rejection of the new Diary object
end

2. 在每个学生页面下显示日记条目。

您可以在学生模型中添加另一个关系。

has_many :diary_entries, through: :diaries

您可以这样访问相关的DiaryEntry对象：

student1 = Student.first
student1.diary_entries