我是铁杆新手，所以我还在努力解决问题，所以非常感谢任何帮助！我正在构建一个定义＆＃34; season＆＃34;并且会有多个＆＃34;舞蹈＆＃34;与那些季节有关。创建一个赛季后，您应该可以选择创建＆＃34; danceclasses＆＃34;所以作为我的季节表演的一部分我有：
<h2>Dance Classes Created</h2>
<%= @seasons.danceclass.each do |danceclass| %>
<p>
但是我收到以下错误：
undefined method `danceclass' for nil:NilClass
我的数据模型是我有一个四季表，一个舞蹈表和一个season_danceclasses表。
我的季节模型是：
class Season < ActiveRecord::Base
has_many :season_class
has_many :danceclass, through: :season_class
end
我的舞蹈课模型如下：
class Danceclass < ActiveRecord::Base
belongs_to :season
has_many :student_class
has_many :student, through: :student_class
end
我对season_danceclass的模型看起来像这样：
class SeasonDanceclasses < ActiveRecord::Base
belongs_to :season
belongs_to :danceclass
end
我的season_controller看起来像这样：
class SeasonsController < ApplicationController
before_action :set_season, only: [:show, :edit, :update, :destroy]
# GET /seasons
# GET /seasons.json
def index
@seasons = Season.all
end
# GET /seasons/1
# GET /seasons/1.json
def show
end
# GET /seasons/new
def new
@season = Season.new
end
# GET /seasons/1/edit
def edit
end
# POST /seasons
# POST /seasons.json
def create
@season = Season.new(season_params)
respond_to do |format|
if @season.save
format.html { redirect_to @season, notice: 'Season was successfully created.' }
format.json { render :show, status: :created, location: @season }
else
format.html { render :new }
format.json { render json: @season.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /seasons/1
# PATCH/PUT /seasons/1.json
def update
respond_to do |format|
if @season.update(season_params)
format.html { redirect_to @season, notice: 'Season was successfully updated.' }
format.json { render :show, status: :ok, location: @season }
else
format.html { render :edit }
format.json { render json: @season.errors, status: :unprocessable_entity }
end
end
end
# DELETE /seasons/1
# DELETE /seasons/1.json
def destroy
@season.destroy
respond_to do |format|
format.html { redirect_to seasons_url, notice: 'Season was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_season
@season = Season.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def season_params
params.require(:season).permit(:season_name, :season_start, :season_end)
end
end
我做错了什么？
编辑：添加Schema.rb
# encoding: UTF-8
# This file is auto-generated from the current state of the database. Instead
# of editing this file, please use the migrations feature of Active Record to
# incrementally modify your database, and then regenerate this schema definition.
#
# Note that this schema.rb definition is the authoritative source for your
# database schema. If you need to create the application database on another
# system, you should be using db:schema:load, not running all the migrations
# from scratch. The latter is a flawed and unsustainable approach (the more migrations
# you'll amass, the slower it'll run and the greater likelihood for issues).
#
# It's strongly recommended that you check this file into your version control system.
ActiveRecord::Schema.define(version: 20160729111417) do
create_table "danceclasses", force: :cascade do |t|
t.string "class_id", limit: 255
t.string "class_name", limit: 255
t.text "class_description", limit: 65535
t.integer "min_students", limit: 4
t.integer "max_students", limit: 4
t.string "category", limit: 255
t.datetime "start_date"
t.datetime "end_date"
t.integer "week_frequency", limit: 4
t.integer "day_frequency", limit: 4
t.string "start_time", limit: 255
t.string "end_time", limit: 255
t.integer "fee", limit: 4
t.string "level", limit: 255
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "season_classes", force: :cascade do |t|
t.integer "season_id", limit: 4
t.integer "danceclass_id", limit: 4
end
create_table "seasons", force: :cascade do |t|
t.string "season_name", limit: 255
t.datetime "season_start"
t.datetime "season_end"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "student_classes", force: :cascade do |t|
t.integer "student_id", limit: 4
t.integer "class_id", limit: 4
end
create_table "students", force: :cascade do |t|
t.string "first_name", limit: 255
t.string "last_name", limit: 255
t.string "student_id", limit: 255
t.datetime "date_of_birth"
t.text "notes", limit: 65535
t.string "gender", limit: 255
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "user_students", force: :cascade do |t|
t.integer "user_id", limit: 4
t.integer "student_id", limit: 4
end
create_table "users", force: :cascade do |t|
t.string "username", limit: 255
t.string "email", limit: 255
t.string "password", limit: 255
t.string "first_name", limit: 255
t.string "last_name", limit: 255
t.string "phone_number", limit: 255
t.datetime "date_of_birth"
t.string "street_1", limit: 255
t.string "street_2", limit: 255
t.string "city", limit: 255
t.string "state", limit: 255
t.string "zipcode", limit: 255
t.boolean "enabled"
t.boolean "is_admin"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
end
答案 0 :(得分：0)
您需要正确更改has_many关联。
class Season < ActiveRecord::Base
has_many :season_classes
has_many :danceclasses, through: :season_class
end
希望这对你有帮助！
答案 1 :(得分：0)
首先，你所采取的关联应该是has_many的复数，
class Season < ActiveRecord::Base
has_many :season_classes
has_many :dance_classes, through: :season_classes
end
class Danceclass < ActiveRecord::Base
belongs_to :season
has_many :student_classes
has_many :students, through: :student_classes
end
class SeasonDanceclasses < ActiveRecord::Base
belongs_to :season
belongs_to :danceclass
end
现在，正如你所说的那个视图是你季节表演动作的季节显示页面，
class SeasonsController < ApplicationController
before_action :set_season, only: [:show, :edit, :update, :destroy]
def index
@seasons = Season.all
end
def show
end
end
您的show方法包含 @season变量，但不包含@seasons ，这是set_season动作中设置的，
so app/views/seasons/show.html.erb is,
这是与您的旧协会
<h2>Dance Classes Created</h2>
<% @season.danceclass.each do |danceclass| %>
-----------
----------
<% end %>
<p></p>
这是更改后的关联
<h2>Dance Classes Created</h2>
<% @season.dance_classes.each do |danceclass| %>
-----------
----------
<% end %>
<p></p>