Question

我正在尝试从其他模型下拉并在索引页面中显示其名称

我有3个表“学生”，“教室”和“教室_学生” 我正在尝试的是，当一个学生被创建时，他应该能够从一个从教室桌子填充的下拉列表中添加教室，在下拉工作的那一刻，但它从下拉列表获得id

如何让课堂名称显示在索引页面

课堂模式

class Classroom < ApplicationRecord
    belongs_to :user
    has_many :classroom_students
    has_many :students, through: :classroom_students
end

学生模型

class Student < ApplicationRecord
    has_many :classroom_students
    has_many :classrooms, through: :classroom_students
    validates :student_fname, presence: true, length: { minimum: 3, maximum: 50 }
end

classroom_student模型

class ClassroomStudent < ApplicationRecord
    belongs_to :classroom
    belongs_to :student
end

学生控制器

def student_params
    params.require(:student).permit(:student_fname, :student_lname, :gender, :dob, :aboriginal, :esl, :special_provisions, :user_id, :classroom_id, :group_id, :active)
end

教室控制器

def classroom_params
  params.require(:classroom).permit(:classroom_name, :classroom_year, :classroom_student)
end

学生观点表

<%= form.select :classroom_id, Classroom.where(:user_id => current_user.id).map {|r| [r.classroom_name, r.id]}  %>

学生索引

目前它是id，但我希望它是教室名称

<td><%= student.classroom_id %>

架构文件

create_table "classroom_students", force: :cascade do |t|
    t.integer "classroom_id"
    t.integer "student_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

create_table "classrooms", force: :cascade do |t|
    t.string "classroom_name"
    t.date "year"
    t.string "classroom_student"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer "users_id"
    t.integer "user_id"
    t.string "classroom_year"
    t.index ["users_id"], name: "index_classrooms_on_users_id"
  end

create_table "students", force: :cascade do |t|
    t.string "student_fname"
    t.string "student_lname"
    t.boolean "gender"
    t.string "dob"
    t.boolean "aboriginal"
    t.boolean "esl"
    t.text "special_provisions"
    t.integer "user_id"
    t.integer "classroom_id"
    t.integer "group_id"
    t.boolean "active"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "classroom_name"
  end

Answer 1

您的关联表示student has many classrooms，但您的数据库架构显示clasroom_id表中也有students。如果您需要将classroom_id与多个student相关联，请先删除classrooms。然后你的选择说：

<%= form.select :classroom_id, Classroom.where(:user_id => current_user.id).map {|r| [r.classroom_name, r.id]}  %>

现在您有多个classrooms与一个student相关联，因此这不起作用，因为classroom_id无效。相反它应该是这样的：

<%= f.select :classroom_ids, Classroom.where(user_id: current_user.id).map { |r| [r.classroom_name, r.id] }, {}, multiple: true %>

这会将多个classrooms与student相关联。

并且不要忘记在强大的参数中添加classroom_ids：

def student_params
  params.require(:student).permit(:student_fname, :student_lname, :gender, :dob, :aboriginal, :esl, :special_provisions, :user_id, :classroom_id, :group_id, :active, :classroom_ids => [])
end

希望这有帮助。

Answer 2

首先，你有一个用户has_many：教室的关联，所以你不能认为你只有一个教室。

您可以使用以下内容获取与用户关联的所有类：

    <%= f.form_for @student do |f| %>
    <%= f.collection_select(:classrrom_id, Classroom.all, :id, :classroom_name,
 {:prompt => "Select your classrooms"}, {:multiple => true}) %>
    <% end %>

在您的students_controller.rb中，您应该将lesson_ids添加到您的参数

def student_params
  params.require(:student).permit(:student_fname, :student_lname, :gender,
 :dob, :aboriginal, :esl, :special_provisions, :user_id, :classroom_id,
 :group_id, :active, :classroom_ids => [])
end

如何在rails中显示名称而不是ID

2 个答案: