Question

第一次问一个问题，不确定我是否做得对，但是这里有。我收到此错误

表单中的第一个参数不能包含nil或为空 /nameofapp/app/views/products/_form.html.erb第1行引出：

以下是我的链接：

查看

<%= form_for(@product) do |f| %>
  <% if @product.errors.any? %>
    <div id="error_explanation">

控制器

  class ProductsController < ApplicationController
before_action :set_product, only: [:show, :edit, :update, :destroy]

# GET /products
# GET /products.json
def index
  @products = Product.all
end

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

# GET /products/new
def new
  @product = Product.new
end

# GET /products/1/edit
def edit
end

# POST /products
# POST /products.json
def create
  @product = Product.new(product_params)

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

# PATCH/PUT /products/1
# PATCH/PUT /products/1.json
def update
  respond_to do |format|
    if @product.update(product_params)
      format.html { redirect_to @product, notice: 'Product was successfully updated.' }
      format.json { render :show, status: :ok, location: @product }
    else
      format.html { render :edit }
      format.json { render json: @product.errors, status: :unprocessable_entity }
    end
  end
end

# DELETE /products/1
# DELETE /products/1.json
def destroy
  @product.destroy
  respond_to do |format|
    format.html { redirect_to products_url, notice: 'Product was successfully destroyed.' }
    format.json { head :no_content }
  end
end

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

  # Never trust parameters from the scary internet, only allow the white list through.
  def product_params
    params.require(:product).permit(:name, :description, :image_url, :colour, :price)
  end

端 #PATCH / PUT / products / 1 #PATCH / PUT /products/1.json def更新 respond_to do | format | if @ product.update（product_params） format.html {redirect_to @product，注意：＆＃39;产品已成功更新。＆＃39; } format.json {render：show，status :: ok，location：@product} 其他 format.html {render：edit} format.json {render json：@ product.errors，status :: unprocessable_entity} 结束结束端

# DELETE /products/1
# DELETE /products/1.json
def destroy
  @product.destroy
  respond_to do |format|
    format.html { redirect_to products_url, notice: 'Product was successfully destroyed.' }
    format.json { head :no_content }
  end
end

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

  # Never trust parameters from the scary internet, only allow the white list through.
  def product_params
    params.require(:product).permit(:name, :description, :image_url, :colour, :price)
  end

端

Answer 1

我认为问题来自edit行动，它没有@product价值

它应该像这样更新

def edit
  @product = Product.find(param[:id])
end

Answer 2

@product为nil，你必须加载它。

您必须在所需的操作中将其加载到控制器中。就像编辑或显示动作一样。

@product = Product.find(params[:id])

或者在set_product中确保你拥有它。

private

def set_product
  @product = Product.find(params[:id])
end

Answer 3

如果我是正确的，您将在index.html.erb中呈现部分内容，如果是，则将控制器中的index操作更改为

def index
  @products = Product.all
  @product = Product.new
end

获取＆＃34;形式中的第一个参数不能包含nil或为空＃34;错误

3 个答案: