在RoR控制器中从html获取数据时出现问题

Question

我在试着做一个产品推车。我希望当我将产品添加到购物车时，能够选择产品的数量。

这是LineItemsController

    class LineItemsController < ApplicationController
  include CurrentCart
  before_action :set_line_item, only: [:show, :edit, :update, :destroy]
  before_action :set_cart, only: [:create]

  def index
    @line_items = LineItem.all
  end

  def show
  end

  def new
    @line_item = LineItem.new
  end

  def edit
  end

  def create
    product = Product.find(params[:product_id])
    @line_item = @cart.add_product(product)
    @line_item.quantity = params['q'].to_i

      if @line_item.save
        redirect_to @line_item.cart, notice: 'Item added to cart.'
      else
        render :new
      end
  end

  def update
      if @line_item.update(line_item_params)
        redirect_to @line_item, notice: 'Line item was successfully updated.'
      else
        render :edit
      end
  end

  def destroy
    @cart = Cart.find(session[:cart_id])
    @line_item.destroy
    redirect_to cart_path(@cart), notice: 'Item successfully removed.'
  end

  private
    def set_line_item
      @line_item = LineItem.find(params[:id])
    end

    def line_item_params
      params.require(:line_item).permit(:product_id, :quantity)
    end
end

这是view/line_item/_form.html.erb

<%= simple_form_for(@line_item) do |f| %>
  <%= f.error_notification %>

  <div class="form-inputs">
    <%= f.association :product %>
    <%= f.association :cart %>
  </div>

  <div class="form-actions">
    <%= f.button :submit %>
  </div>
<% end %>

这是view/product/show.html.erb

    <% content_for :body_class, 'bg-light' %>

<section class="section instrument-show">
  <div class="columns">
    <div class="column is-8">
      <%= render 'shared/breadcrumb', category: @product.category %>
      <h1 class="title is-2"><%= @product.title %></h1>

      <!--ul class="pv1">
        <%# if @product.brand? %>
        <li class="inline-block pr3"><%#= @product.brand %></li-->
        <%# end %>

        <!--li class="inline-block pr3"><%#= @product.model %></li-->

        <%# if @product.condition? %>
        <!--li class="inline-block pr3"><%#= @product.condition %></li>
        <%# end %>
      </ul-->

      <div class="feature-image">
        <%= image_tag(@product.image_url(:default).to_s) %>
      </div>

      <div class="content pa4 mt3 bg-white border-radius-3">

      <h3 class="subtitle is-4">Description</h3>
      <%= @product.description %>


      <h3 class="subtitle is-4 pt5">Product Specs</h3>

      <table class="table is-narrow">
        <% if @product.category.present? %>
        <tr>
          <td class="has-text-weight-bold">Category:</td>
          <td><%= link_to @product.category.name, @product.category %></td>
        </tr>
        <% end %>

        <%# if @product.finish %>
          <tr>
            <td class="has-text-weight-bold">Finish:</td>
            <td><%#= @product.finish %></td>
          </tr>
        <%# end %>

        <tr>
          <td class="has-text-weight-bold">Model:</td>
          <td><%#= @product.model %></td>
        </tr>
      </table>
    </div>
    </div>
    <div class="column is-3 is-offset-1">
      <div class="bg-white pa4 border-radius-3">
        <h4 class="title is-5 has-text-centered"><%= number_to_currency(@product.price) %></h4>
        <p class="has-text-centered mb4">Sold by <%#= @product.user.name %></p>

        <form>
          <input type="number" name="q" min="1" max="50" step="1" class="input label">
        </form>


        <%= button_to 'Add to cart', line_items_path(product_id: @product), class: 'button is-warning add-to-cart' %>
      </div>
    </div>
  </div>

  <% if user_signed_in? && current_user.admin? %>
    <%= link_to 'Edit', edit_admin_product_path(@product), class: 'button' %>
  <% end %>
</section>

现在，在这个字符串中，@line_item.quantity = params['q'].to_i来自

<form>
  <input type="number" name="q" min="1" max="50" step="1" class="input label">
</form>

我得到了“零”，我现在非常不知道我应该怎么做才能得到实际的数字。

附注:这是view/line_item/new.html.erb

<h1>New Line Item</h1>

<%= render 'form', line_item: @line_item %>

<%= link_to 'Back', line_items_path %>

Answer 1

new.html.erb是输入你的数据，如果你提交了，数据就会流动到你的控制器里面去创建方法，同时show只是展示数据，你不能在show里面输入表单，我建议试着把new.html.erb的q部分放到simple_form_for标签里面，因为它是数字，你可以使用number_field rails tag helper作为示例，名字:q，范围在1之间。50步骤1，下面是可能对您的问题有所帮助的示例

当您从new.html.erb提交时，您将收到params:q作为参数的一部分，并使用create方法保存它

<%= simple_form_for(@line_item) do |f| %>
  <%= f.error_notification %>

  <%= number_field(:q, in: 1.0..50.0, step: 1) %>

  <div class="form-inputs">
    <%= f.association :product %>
    <%= f.association :cart %>
  </div>

  <div class="form-actions">
    <%= f.button :submit %>
  </div>
<% end %>