在Rails 4應用程序中使用強參數未發現參數錯誤

Question

我一直在努力弄清楚爲什麼我會收到以下錯誤。看起來好像是因爲有一個fruit_controller，參數：fruit應該存在。任何幫助將非常感謝，因爲這使我在過去的五個小時裏一直在困擾着我。

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__1__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 

這是fruits_controller.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 

這裏的水果/ index.html.erb

<h1>New fruit</h1> 

<%= render 'form' %> 

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

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 %> 

我沒有索引視圖的問題，但它只發生s當我嘗試從索引視圖創建新的水果時：

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

謝謝！

Answer 1

發生此錯誤是因爲您在new操作中調用fruit_params。您應該只在new動作中使用build對象，以便他們爲表單做好準備。

這是你現在有代碼：

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

這幾乎是功能......唯一的問題是fruit_params調用，預計params[:fruit]可用，但不是因爲你」重新使得使用該助手到路徑的請求：

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

有傳遞沒有參數那裏，所以params[:fruit]將是你的new行動缺席。

更改new動作的代碼如下：

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

，這將建立@fruit變量的形式在app/views/fruits/_form.html.erb使用。