Ruby on rails 为什么我必须在我的Show动作中包含@link=link.find（params[：id]）？_Ruby On Rails_Controller_Scaffolding

Ruby on rails 为什么我必须在我的Show动作中包含@link=link.find（params[：id]）？

ruby-on-rails

Ruby on rails 为什么我必须在我的Show动作中包含@link=link.find（params[：id]）？,ruby-on-rails,controller,scaffolding,Ruby On Rails,Controller,Scaffolding,我正在制作reddit的一个模型，在这个模型中，我以一个表单提交url和标题，然后数据库应该被填充，我们应该被带到一个展示页面，以查看我们提交的链接和标题我的问题是为什么我必须在我的控制器中包含这个 def show @link = Link.find(params[:id]) end 如果我删除@link=link.find（params[：id]）我的显示不起作用我得到以下错误： NoMethodError in Links#show 在这条线上 <%= @

我正在制作reddit的一个模型，在这个模型中，我以一个表单提交url和标题，然后数据库应该被填充，我们应该被带到一个展示页面，以查看我们提交的链接和标题

我的问题是为什么我必须在我的控制器中包含这个

  def show  
    @link = Link.find(params[:id])
  end

如果我删除

@link=link.find（params[：id]）

我的显示不起作用

我得到以下错误：

NoMethodError in Links#show

在这条线上

<%= @link.title %>

我正在与另一个项目进行比较，在这个项目中，我为类似的东西生成了一个scaffold，我只有私有方法，不需要在我的show action中使用

@link=link.find（params[:id]）

这是我的完整控制器代码：

class LinksController < ApplicationController

  def index
    @link = Link.all
  end

  def new
    @link = Link.new
  end

  def create
    @link = Link.new(link_params)

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

  def show  
    @link = Link.find(params[:id])
  end


private
  def set_link
    @link = Link.find(params[:id])
  end
  def link_params
    params.require(:link).permit(:title, :url)
  end


end

类链接控制器


这是我生成的脚手架的完整控制器：
class HighScoresController < ApplicationController
  before_action :set_high_score, only: [:show, :edit, :update, :destroy]

  # GET /high_scores
  # GET /high_scores.json
  def index
    @high_scores = HighScore.all
  end

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

  # GET /high_scores/new
  def new
    @high_score = HighScore.new
  end

  # GET /high_scores/1/edit
  def edit
  end

  # POST /high_scores
  # POST /high_scores.json
  def create
    @high_score = HighScore.new(high_score_params)

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

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

  # DELETE /high_scores/1
  # DELETE /high_scores/1.json
  def destroy
    @high_score.destroy
    respond_to do |format|
      format.html { redirect_to high_scores_url }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def high_score_params
      params.require(:high_score).permit(:game, :score)
    end
end

class HighScoresController < ApplicationController
  before_action :set_high_score, only: [:show, :edit, :update, :destroy]

class HighScoresController

为什么生成的脚手架在我的show action中没有@link=link.find（params[：id]）
，而我自己的项目却没有？
您缺少生成的脚手架的控制器类中的第一行：
class HighScoresController < ApplicationController
  before_action :set_high_score, only: [:show, :edit, :update, :destroy]

  # GET /high_scores
  # GET /high_scores.json
  def index
    @high_scores = HighScore.all
  end

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

  # GET /high_scores/new
  def new
    @high_score = HighScore.new
  end

  # GET /high_scores/1/edit
  def edit
  end

  # POST /high_scores
  # POST /high_scores.json
  def create
    @high_score = HighScore.new(high_score_params)

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

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

  # DELETE /high_scores/1
  # DELETE /high_scores/1.json
  def destroy
    @high_score.destroy
    respond_to do |format|
      format.html { redirect_to high_scores_url }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def high_score_params
      params.require(:high_score).permit(:game, :score)
    end
end

class HighScoresController < ApplicationController
  before_action :set_high_score, only: [:show, :edit, :update, :destroy]

在执行show
操作之前，调用set\u link
函数。
您缺少生成的脚手架的控制器类中的第一行：
class HighScoresController < ApplicationController
  before_action :set_high_score, only: [:show, :edit, :update, :destroy]

  # GET /high_scores
  # GET /high_scores.json
  def index
    @high_scores = HighScore.all
  end

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

  # GET /high_scores/new
  def new
    @high_score = HighScore.new
  end

  # GET /high_scores/1/edit
  def edit
  end

  # POST /high_scores
  # POST /high_scores.json
  def create
    @high_score = HighScore.new(high_score_params)

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

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

  # DELETE /high_scores/1
  # DELETE /high_scores/1.json
  def destroy
    @high_score.destroy
    respond_to do |format|
      format.html { redirect_to high_scores_url }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def high_score_params
      params.require(:high_score).permit(:game, :score)
    end
end

class HighScoresController < ApplicationController
  before_action :set_high_score, only: [:show, :edit, :update, :destroy]

在执行show
操作之前，调用set\u link
函数。
您缺少生成的脚手架的控制器类中的第一行：
class HighScoresController < ApplicationController
  before_action :set_high_score, only: [:show, :edit, :update, :destroy]

  # GET /high_scores
  # GET /high_scores.json
  def index
    @high_scores = HighScore.all
  end

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

  # GET /high_scores/new
  def new
    @high_score = HighScore.new
  end

  # GET /high_scores/1/edit
  def edit
  end

  # POST /high_scores
  # POST /high_scores.json
  def create
    @high_score = HighScore.new(high_score_params)

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

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

  # DELETE /high_scores/1
  # DELETE /high_scores/1.json
  def destroy
    @high_score.destroy
    respond_to do |format|
      format.html { redirect_to high_scores_url }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def high_score_params
      params.require(:high_score).permit(:game, :score)
    end
end

class HighScoresController < ApplicationController
  before_action :set_high_score, only: [:show, :edit, :update, :destroy]

在执行show
操作之前，调用set\u link
函数。
您缺少生成的脚手架的控制器类中的第一行：
class HighScoresController < ApplicationController
  before_action :set_high_score, only: [:show, :edit, :update, :destroy]

  # GET /high_scores
  # GET /high_scores.json
  def index
    @high_scores = HighScore.all
  end

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

  # GET /high_scores/new
  def new
    @high_score = HighScore.new
  end

  # GET /high_scores/1/edit
  def edit
  end

  # POST /high_scores
  # POST /high_scores.json
  def create
    @high_score = HighScore.new(high_score_params)

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

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

  # DELETE /high_scores/1
  # DELETE /high_scores/1.json
  def destroy
    @high_score.destroy
    respond_to do |format|
      format.html { redirect_to high_scores_url }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def high_score_params
      params.require(:high_score).permit(:game, :score)
    end
end

class HighScoresController < ApplicationController
  before_action :set_high_score, only: [:show, :edit, :update, :destroy]

在执行show
操作之前，调用set\u link
函数。
您需要将实例变量@link的值设置为
@link = Link.find(params[:id])

在show action中，因为在link
的show
视图中，您将显示特定链接对象（@link）的详细信息，如
并从显示、编辑、更新和销毁
操作（如果有）中删除对@link=link.find（params[：id]）
的调用
使用only
选项设置before\u action
将导致在执行所列操作之前调用set\u link
方法
例如：如果您访问某个链接的显示url，则首先会调用set_link，然后调用该显示操作（因为显示操作位于：only列表中）
请注意，HighScoresController
也设置了相同的内容（在\u操作之前：设置\u high\u score
），这就是为什么避免了对@highscore=highscore.find（params[：id]
的冗余调用。
您需要将实例变量@link
的值设置为
@link = Link.find(params[:id])

在show action中，因为在link
的show
视图中，您将显示特定链接对象（@link）的详细信息，如
并从显示、编辑、更新和销毁
操作（如果有）中删除对@link=link.find（params[：id]）
的调用
使用only
选项设置before\u action
将导致在执行所列操作之前调用set\u link
方法
例如：如果您访问某个链接的显示url，则首先会调用set_link，然后调用该显示操作（因为显示操作位于：only列表中）
注意