Ruby on rails nil的未定义方法“贷款金额”：NilClass

我正在使用ruby 2.2.2p95 2015-04-13修订版50295[i686 linux]和Rails 4.2.1进行珠宝贷款申请，因为我有两种型号：

1jewelloan.rb 2jltransaction.rb

我已添加外键jewelloan\u id以获取jltransactions表中的贷款金额。其中，as loan_amount是贷款表中的一个字段

我的问题是外键关系不起作用。我已经搜索了许多stackoverflow问题来解决这个问题，但这些问题都不起作用

我已经附上了我的模型，视图，控制器和一切。请告诉我哪里出错了

jewelloan.rb

请给出一些使用外键的想法

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谢谢…

您的关系可能返回零结果。 试一试

你可以试试这个：

<%= jlt.text_field :loan_amount, :disabled => true, :value => @jltransaction.jewelloan.try(:loan_amount) if @jltransaction && @jltransaction.jewelloan %>

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现在显示了该字段，但无法获取贷款金额。您是否确保@jltransaction对象具有与之关联的jewelloan记录？我的jltransactions表中的字段贷款金额仍然为空值。您是否可以粘贴@jltransaction.jewelloan？jewelloan加载0.3ms的结果从jewelloans中选择jewelloans.*其中jewelloans.id=？LIMIT 1[[id，4]]在2015-05-29 14:56:02+0530开始获取127.0.0.1的/jltransactions/new？id=4，由jltransactioncontrollernew作为HTML参数处理：{id=>4}在我尝试之后：由jltransactioncontrollercreate作为HTML jltransaction=>{jewelloan\u id=>}2146ms ActiveRecord中已完成500个内部服务器错误：104.7ms NameError未定义的局部变量或方法jewelloan_参数用于：app/controllers/jltransactions_controller.rb:11:in create'在jltransactions_控制器中添加强参数，如jewelloan_属性：[属性….]在jltransactions_控制器中：@jewelloan=@jltransaction.jewelloansjewelloan_参数此行正确吗？添加了强参数，但结果仍然是jltransactions_控制器中相同的强参数，它应该是多个jewelloans_属性：[属性….]

 class Jltransaction < ActiveRecord::Base

    attr_accessor :loan_amount

    attr_accessible :loan_amount

    belongs_to :jewelloan 

    attr_accessible :transaction_date, :transaction_amount, :transaction_mode, :transaction_type, :particulars, :comments, :jewelloan_id

 end

 class JewelloansController < ApplicationController

  def new
    @jewelloan = Jewelloan.new
  end

  def create
    @jewelloan = Jewelloan.create(jewelloan_params)
    if @jewelloan.save
      flash[:success] = "Special JL was successfully created"
      redirect_to @jewelloan
    else
      flash[:danger] = "Special Jewel Loan was not created"
      render 'new'
    end
  end

  private

    def jewelloan_params
      params.require(:jewelloan).permit(:account_number, :customer_name, :customer_address, :amount, :interest_rate, :opened_on, :due_date, :amount_due, :jewel, :no_of_items, :gross_weight, :net_weight, :appraised_amount, :loan_amount, :transaction_mode, :transaction_type, :particulars, :comments, :close_date, :no_of_days, :jltransactions_attributes)
    end

  end

 class JltransactionsController < ApplicationController

   def new    
     @jltransaction = Jltransaction.new
     @jewelloan = Jewelloan.new
   end

   def create
     @jltransaction = Jltransaction.create(jltransaction_params)  
     @jewelloan = @jltransaction.jewelloans(jewelloan_params)  
     if @jltransaction.save
       flash[:success] = "Transaction created"
       redirect_to @jltransaction
     else
       flash[:danger] = "Transaction was not created"
       render 'new'
     end
   end

 private
  def jltransaction_params
    params.require(:jltransaction).permit(:transaction_date, :transaction_amount, :transaction_mode, :transaction_type, :particulars, :comments, :jewelloan_id)
  end

 end

 <%= form_for @jltransaction do |jlt| %>

 <%= jlt.hidden_field :jewelloan_id, :value => @jewelloan.id %>

 <% if @jltransaction.errors.any? %>

 <h2>Transaction Failed</h2>
 <ul>

 <% @jltransaction.errors.full_messages.each do |error| %>

 <li><%= error %></li>

 <% end %>

 </ul>

 <% end %>    

 <%= jlt.label :loan_amount %>
 for<%= jlt.text_field :loan_amount, :disabled => true, :value => @jltransaction.jewelloan.try(:loan_amount) %>

 <%= jlt.label :transaction_amount %>
 <%= jlt.text_field :transaction_amount %>

 <%= jlt.submit "Submit Transaction", class: "btn btn-success" %> 

  <% end %>

 Completed 500 Internal Server Error in 34ms (ActiveRecord: 0.0ms)

 ActionView::Template::Error (undefined method `loan_amount' for nil:NilClass):

@jltransaction.jewelloan.try(:loan_amount)

<%= jlt.text_field :loan_amount, :disabled => true, :value => @jltransaction.jewelloan.try(:loan_amount) if @jltransaction && @jltransaction.jewelloan %>