ruby-on-rails – 将多步骤表单向导的第一步渲染为另一个控制器

我正在渲染Item的显示页面中的第一步：

<%= render "/wizards/step1" %>

@trade_wizard在实例化@trade的特殊模型中处理,然后从每个步骤连续继承验证：

module Wizard
  module Trade
    STEPS = %w(step1 step2 step3).freeze

    class Base
      include ActiveModel::Model
      attr_accessor :trade

      delegate *::Trade.attribute_names.map { |attr| [attr,"#{attr}="] }.flatten,to: :trade

      def initialize(trade_attributes)
        @trade = ::Trade.new(trade_attributes)
      end
    end

    class Step1 < Base
      validates :trade_requester_id,:trade_recipient_id,:wanted_item_id,presence: true
      validates :shares,numericality: { only_integer: true,greater_than_or_equal_to: 0,less_than_or_equal_to: :max_shares }

      def max_shares
        @trade.wanted_item.shares
      end

    end

    class Step2 < Step1
      validates :collateral_item_id,presence: true
    end

    class Step3 < Step2
      validates :agreement,presence: true
    end
  end
end

然后我的WizardsController在每一步上运行验证并保存对象：

class WizardsController < ApplicationController
  before_action :load_trade_wizard,except: %i(validate_step)

  def validate_step
    current_step = params[:current_step]

    @trade_wizard = wizard_trade_for_step(current_step)
    @trade_wizard.trade.attributes = trade_wizard_params
    session[:trade_attributes] = @trade_wizard.trade.attributes

    if @trade_wizard.valid?
      next_step = wizard_trade_next_step(current_step)
      create and return unless next_step

      redirect_to action: next_step
    else
      render current_step
    end
  end

  def create
    if @trade_wizard.trade.save
      session[:trade_attributes] = nil
      redirect_to root_path,notice: 'Trade succesfully created!'
    else
      redirect_to({ action: Wizard::Trade::STEPS.first },alert: 'There were a problem when creating the trade.')
    end
  end

  private

  def load_trade_wizard
    @trade_wizard = wizard_trade_for_step(action_name)
  end

  def wizard_trade_next_step(step)
    Wizard::Trade::STEPS[Wizard::Trade::STEPS.index(step) + 1]
  end

  def wizard_trade_for_step(step)
    raise InvalidStep unless step.in?(Wizard::Trade::STEPS)

    "Wizard::Trade::#{step.camelize}".constantize.new(session[:trade_attributes])
  end

  def trade_wizard_params
    params.require(:trade_wizard).permit(:trade_requester_id,:collateral_item_id,:shares,:agreement)
  end

  class InvalidStep < StandardError; end
end

在我的路线我有

resource :wizard do
    get :step1
    get :step2
    get :step3
    post :validate_step
end

我通过此设置获得的错误是表单中的第一个参数不能包含nil或为空.我知道为什么会发生这种情况 – 我需要在ItemsController#show中定义@trade_wizard,我还没有这样做,因为这只会导致我从WizardsController复制代码.我不需要任何人为我做我的工作,我只需要一个指针,指出我如何能够解决这个问题.