获取“表单中的第一个参数不能包含nil或为空”错误

Question

第一次问一个问题，我不确定我是否做对了，但现在开始。我得到了这个错误

表单中的第一个参数不能包含nil或为空/nameofapp/app/views/products/\u表单。html。第#1行引出的erb：

以下是我的链接：

看法

<%= 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

结束#PATCH/PUT /products/1#PATCH/PUT /products/1.jsondef更新respond_to|格式|[e-mail]（product_params）format.html{redirect_to@产品，通知：'产品已成功更新.' } format.json{渲染：显示，状态::确定，位置：@产品}其他format.html{渲染：编辑}format.json{渲染json：@product.errors，状态::unprocessable_entity}结束结束结束

# 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

终止

Answer 1

@产品为零，您必须加载它。

您必须以所需的动作将其加载到控制器中。就像在编辑或显示动作中一样。

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

或者确保在set_产品中您拥有它。

private

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

Answer 2

如果我是正确的，您正在索引中渲染部分。html。erb，如果是，则将控制器中的索引操作更改为以下

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

Answer 3

我认为问题来自编辑操作，它没有@产品价值

应该更新成这样的

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