Ruby on rails 4 使用强参数在Rails 4应用程序中找不到参数错误

我一直在努力弄清楚为什么会出现以下错误。似乎由于有一个水果控制器，参数：水果应该存在。任何帮助都将不胜感激，因为在过去的五个小时里，这已经把我逼疯了

ActionController::ParameterMissing in FruitsController#new
param not found: fruit

Extracted source (around line #80):
78
79
80
81
82

    def fruit_params
      params.require(:fruit).permit(:name, :color)
    end
end

Rails.root: C:/Users/Guy/code/food-master

Application Trace | Framework Trace | Full Trace
actionpack (4.0.0) lib/action_controller/metal/strong_parameters.rb:173:in `require'
app/controllers/fruits_controller.rb:80:in `fruit_params'
app/controllers/fruits_controller.rb:24:in `new'
actionpack (4.0.0) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (4.0.0) lib/abstract_controller/base.rb:189:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (4.0.0) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (4.0.0) lib/active_support/callbacks.rb:413:in `_run__564231598__process_action__callbacks'
activesupport (4.0.0) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.0) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
activesupport (4.0.0) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.0.0) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.0.0) lib/active_support/notifications.rb:159:in `instrument'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/params_wrapper.rb:245:in `process_action'
activerecord (4.0.0) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (4.0.0) lib/abstract_controller/base.rb:136:in `process'
actionpack (4.0.0) lib/abstract_controller/rendering.rb:44:in `process'
actionpack (4.0.0) lib/action_controller/metal.rb:195:in `dispatch'
actionpack (4.0.0) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
actionpack (4.0.0) lib/action_controller/metal.rb:231:in `block in action'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:80:in `call'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:80:in `dispatch'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:48:in `call'
actionpack (4.0.0) lib/action_dispatch/journey/router.rb:71:in `block in call'
actionpack (4.0.0) lib/action_dispatch/journey/router.rb:59:in `each'
actionpack (4.0.0) lib/action_dispatch/journey/router.rb:59:in `call'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:655:in `call'
rack (1.5.2) lib/rack/etag.rb:23:in `call'
rack (1.5.2) lib/rack/conditionalget.rb:25:in `call'
rack (1.5.2) lib/rack/head.rb:11:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/flash.rb:241:in `call'
rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context'
rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/cookies.rb:486:in `call'
activerecord (4.0.0) lib/active_record/query_cache.rb:36:in `call'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
activerecord (4.0.0) lib/active_record/migration.rb:369:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.0.0) lib/active_support/callbacks.rb:373:in `_run__1012308376__call__callbacks'
activesupport (4.0.0) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.0) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/reloader.rb:64:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.0.0) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.0.0) lib/rails/rack/logger.rb:21:in `block in call'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `block in tagged'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:25:in `tagged'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `tagged'
railties (4.0.0) lib/rails/rack/logger.rb:21:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.0.0) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/static.rb:64:in `call'
railties (4.0.0) lib/rails/engine.rb:511:in `call'
railties (4.0.0) lib/rails/application.rb:97:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'
Request

Parameters:

{"food_id"=>"1"}
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Response

Headers:

None

这是您的控制器.rb：

class fruitsController < ApplicationController
  before_action :set_fruit, only: [:show, :edit, :update, :destroy]

  # GET /fruits
  # GET /fruits.json
  def index
    @food = Food.find(params[:food_id])
    @fruits = @food.fruits.all
  end

  # GET /fruits/1
  # GET /fruits/1.json
  def show
    @fruit = fruit.find(params[:id])
    respond_to do |format|
      format.html
      format.json {render json: @fruit}
    end
  end

  # GET /fruits/new
  def new
    @food = Food.find(params[:food_id])
    @fruit = @food.fruits.new(fruit_params)
  end

  # GET /fruits/1/edit
  def edit
  end

  # POST /fruits
  # POST /fruits.json
  def create
    @food = Food.find(params[:food_id])
    @fruit = @food.fruits.create(fruit_params)

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

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

  # DELETE /fruits/1
  # DELETE /fruits/1.json
  def destroy
    @fruit.destroy
    respond_to do |format|
      format.html { redirect_to fruits_url }
      format.json { head :no_content }
    end
  end

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

    def fruit_params
      params.require(:fruit).permit(:name,:color)
    end
end

class水果控制器

这里是fruits/index.html.erb

<h1>New fruit</h1>

<%= render 'form' %>

<%= link_to 'Back', food_fruit_path(@food) %>

新水果

和水果/_form.html.erb

<%= form_for(@fruit) do |f| %>
  <% if @fruit.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@fruit.errors.count, "error") %> prohibited this fruit from being saved:</h2>

      <ul>
      <% @fruit.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="form-group">
    <%= f.label :name %><br>
    <%= f.text_field :name, :class => "form-control" %>
  </div>

  <div class="form-group">
    <%= f.label :color %><br>
    <%= f.number_field :color, :class => "form-control" %>
  </div>
  <div class="actions">
    <%= f.submit "Save fruit", :class => "btn btn-success" %>
  </div>
<% end %>

禁止保存此水果：





“表单控件”%>


“表单控件”%>
“btn btn成功”%>

我对索引视图没有任何问题，但它只在我尝试从索引视图创建新结果时发生：

 <%= link_to 'New Fruit', new_food_fruit_path %>

---

谢谢大家!

发生此错误是因为您在

new

操作中调用了

fruit_params

。您应该只在

new

操作中

build

对象，以便为表单做好准备

这是您现在拥有的代码：

@fruit = @food.fruits.new(fruit_params)

这几乎是功能性的。。。唯一的问题是

fruit\u params

调用，它期望

params[：fruit]

可用，但这并不是因为您正在使用此帮助程序向该路径发出请求：

<%= link_to 'New Fruit', new_food_fruit_path %>

---

这将设置

@fruit

变量，以便在

app/views/fruits/_form.html.erb

的表单中使用。请向我们显示该视图。对此表示抱歉！我以前从来没有给全面的RoR找过麻烦。希望我能掌握窍门！谢谢你的回复！我已经听从了你的建议，我想我理解了“新”对你的解释有什么作用。看起来我也越来越接近了，但现在我收到了一条不同的错误消息，如下所示：

NoMethodError in fruitscocontroller#new undefined method'[]，用于nil:NilClass def new@food=food.find（params[：food\u id]）@fruit=@food.fruits.build end

def new
  @food = Food.find(params[:food_id])
  @fruit = @food.fruits.new
end