創建評論時不保存模型ID。如何正確保存？

Question

我有三個模型設置。用戶，指南和評論。用戶有許多指南和評論。指南屬於用戶，並有很多評論。評論屬於用戶和指南。

當我在控制檯中運行Comment.last.user時，它會返回與用戶有關的信息。但是，當我在控制檯中運行Comment.last.guide時，它將返回nil。創建評論時出現問題。

這些模型都具有經典的has_many和belongs_to關係設置，所以我會從這裏省略這些關係。以下是評論控制器：

class CommentsController < ApplicationController 
    before_action :set_comment, only: [:show, :edit, :update, :destroy] 

    # GET /comments 
    # GET /comments.json 
    def index 
    @comments = Comment.all 
    end 

    # GET /comments/1 
    # GET /comments/1.json 
    def show 
    end 

    # GET /comments/new 
    def new 
    @comment = Comment.new 
    end 

    # GET /comments/1/edit 
    def edit 
    end 

    # POST /comments 
    # POST /comments.json 
    def create 
    @comment = current_user.comments.build(comment_params) 


    respond_to do |format| 
     if @comment.save 
     format.html { redirect_to :back, notice: 'Comment was successfully created.' } 
     format.json { render action: 'show', status: :created, location: @comment } 
     else 
     format.html { render action: 'new' } 
     format.json { render json: @comment.errors, status: :unprocessable_entity } 
     end 
    end 
    end 

    # PATCH/PUT /comments/1 
    # PATCH/PUT /comments/1.json 
    def update 
    respond_to do |format| 
     if @comment.update(comment_params) 
     format.html { redirect_to @comment, notice: 'Comment was successfully updated.' } 
     format.json { head :no_content } 
     else 
     format.html { render action: 'edit' } 
     format.json { render json: @comment.errors, status: :unprocessable_entity } 
     end 
    end 
    end 

    # DELETE /comments/1 
    # DELETE /comments/1.json 
    def destroy 
    @comment.destroy 
    respond_to do |format| 
     format.html { redirect_to comments_url } 
     format.json { head :no_content } 
    end 
    end 

    private 
    # Use callbacks to share common setup or constraints between actions. 
    def set_comment 
     @comment = Comment.find(params[:id]) 
    end 

    # Never trust parameters from the scary internet, only allow the white list through. 
    def comment_params 
     params.require(:comment).permit(:body, :user_id, :guide_id) 
    end 
end 

以下是評論的遷移：

class CreateComments < ActiveRecord::Migration 
    def change 
    create_table :comments do |t| 
     t.text :body 
     t.references :user, index: true 
     t.references :guide, index: true 

     t.timestamps 
    end 
    end 
end 

日誌輸出生成註釋時：

Started POST "/comments" for 127.0.0.1 at 2014-01-08 08:30:54 -0500 
Processing by CommentsController#create as HTML 
    Parameters: {"utf8"=>"✓", "authenticity_token"=>"D2BvBIgU+tniZvr2NgQE/TpHY6J2xHOUm701jqTcJ9A=", "comment"=>{"body"=>"NitinJ Sample Comment", "user_id"=>"some value", "guide_id"=>"some value"}, "commit"=>"Create Comment"} 
    User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = 1 ORDER BY "users"."id" ASC LIMIT 1 
    (0.1ms) begin transaction 
    SQL (21.7ms) INSERT INTO "comments" ("body", "created_at", "guide_id", "updated_at", "user_id") VALUES (?, ?, ?, ?, ?) [["body", "NitinJ Sample Comment"], ["created_at", Wed, 08 Jan 2014 13:30:54 UTC +00:00], ["guide_id", 0], ["updated_at", Wed, 08 Jan 2014 13:30:54 UTC +00:00], ["user_id", 1]] 
    (21.0ms) commit transaction 
Redirected to http://localhost:3000/guides/1-attack 
Completed 302 Found in 53ms (ActiveRecord: 43.1ms) 


Started GET "/guides/1-attack" for 127.0.0.1 at 2014-01-08 08:30:54 -0500 
Processing by GuidesController#show as HTML 
    Parameters: {"id"=>"1-attack"} 
    Guide Load (0.2ms) SELECT "guides".* FROM "guides" WHERE "guides"."id" = ? LIMIT 1 [["id", "1-attack"]] 
    CACHE (0.0ms) SELECT "guides".* FROM "guides" WHERE "guides"."id" = ? LIMIT 1 [["id", "1-attack"]] 
    User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] 
    Comment Load (0.2ms) SELECT "comments".* FROM "comments" WHERE "comments"."guide_id" = ? [["guide_id", 1]] 
    CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] 
    CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] 
    CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] 
    CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] 
    CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] 
    CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] 
    CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] 
    CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] 
    User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = 1 ORDER BY "users"."id" ASC LIMIT 1 
    Rendered comments/_form.html.erb (6.6ms) 
    Rendered guides/show.html.erb within layouts/application (18.9ms) 
DEPRECATION WARNING: Calling #sum with a block is deprecated and will be removed in Rails 4.1. If you want to perform sum calculation over the array of elements, use `to_a.sum(&block)`. (called from _app_views_layouts__navbar_html_erb__2351226726967046587_2202447400 at /Users/DylanRichards/Desktop/runescapeguides/app/views/layouts/_navbar.html.erb:35) 
    Guide Load (0.2ms) SELECT "guides".* FROM "guides" WHERE "guides"."user_id" = ? [["user_id", 1]] 
    (0.2ms) SELECT COUNT(*) FROM "votes" WHERE "votes"."votable_id" = ? AND "votes"."votable_type" = ? AND "votes"."vote_flag" = 't' AND "votes"."vote_scope" IS NULL [["votable_id", 1], ["votable_type", "Guide"]] 
    (0.2ms) SELECT COUNT(*) FROM "votes" WHERE "votes"."votable_id" = ? AND "votes"."votable_type" = ? AND "votes"."vote_flag" = 'f' AND "votes"."vote_scope" IS NULL [["votable_id", 1], ["votable_type", "Guide"]] 
    Rendered layouts/_navbar.html.erb (7.4ms) 
Completed 200 OK in 54ms (Views: 47.8ms | ActiveRecord: 1.5ms) 

其次日誌輸出

Started POST "/guides/1-attack/comments" for 127.0.0.1 at 2014-01-08 08:52:29 -0500 
Processing by CommentsController#create as HTML 
    Parameters: {"utf8"=>"✓", "authenticity_token"=>"D2BvBIgU+tniZvr2NgQE/TpHY6J2xHOUm701jqTcJ9A=", "comment"=>{"body"=>"Another sample NitinJ comment.", "user_id"=>"some value", "guide_id"=>"some value"}, "commit"=>"Create Comment", "guide_id"=>"1-attack"} 
Completed 500 Internal Server Error in 69ms 

NoMethodError (undefined method `[]=' for nil:NilClass): 
    app/controllers/comments_controller.rb:27:in `create' 


    Rendered /Users/DylanRichards/.rvm/gems/ruby-2.0.0-p247/gems/actionpack-4.0.2/lib/action_dispatch/middleware/templates/rescues/_source.erb (1.0ms) 
    Rendered /Users/DylanRichards/.rvm/gems/ruby-2.0.0-p247/gems/actionpack-4.0.2/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.7ms) 
    Rendered /Users/DylanRichards/.rvm/gems/ruby-2.0.0-p247/gems/actionpack-4.0.2/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (1.5ms) 
    Rendered /Users/DylanRichards/.rvm/gems/ruby-2.0.0-p247/gems/actionpack-4.0.2/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (21.7ms) 

Answer 1

試這<%= f.association :guide, :as => :hidden, :input_html => { :value => @guide.id }%>