使用 DataMapper 在 Rails 3 中保存嵌套资源表单时出现“NoMethodError”错误

Question

在我的控制器中，我有：

def index
 @owner = current_user
 @accounts = @owner.accounts.all( :name.not => nil )
 @aliases = @owner.aliases.all( :id.not => nil )
 @transfer = @accounts.transfers.new()
end

def create 
@owner = current_user
 @account = @owner.accounts.first(:id => params[:account_id])
 @alias_out = @owner.aliases.first( :id => params[:alias_from]) 
 @alias_in = Alias.first( :id => params[:alias_to]) 

   @transfer =  @account.transfers.create(params[:transfer])  
                @alias_in.update(:transfers_in => params[:transfer]) 
                @alias_out.update(:transfers_out => params[:transfer]) 

在我看来：

<div id="accounts_list">
   <h2>Your accounts</h2>
    <% @accounts.each do |acc| %>
    <div class="each_element">
      <h3><u><%= acc.name%></u></h3>
      <b>Available money: <u><%= acc.value%> <%=acc.currency%></u></b>
      <div id="create_account">
         <h2>Create an transfer</h2>
    <%= form_for([acc, @transfer]) do |trans_form|%>
         <%= trans_form.label :amount %>
        <%= trans_form.text_field :amount %></br>
        <%= trans_form.fields_for :alias_from do |alias_from|%>
        <%= alias_from.label :alias_from %>
        <%= alias_from.collection_select :id, @aliases, :id, :id %> </br>
        <%end%>
        <%= trans_form.fields_for :alias_to do |alias_to|%>
        <%= alias_to.label :alias_to %>
        <%= alias_to.text_field :id %></br>
        <%end%>
        <%= trans_form.text_area :comment, :rows=>5 %></br>
        <%= trans_form.submit :value => "Transfer" %>
         <%end%>
        </div>
    </div>

    <% end %>
</div>
</div>

在我的模型中

class Transfer
  include DataMapper::Resource


  belongs_to :account
  belongs_to :alias_from, "Alias", :key =>true
  belongs_to :alias_to, "Alias", :key =>true 



   property :id, Serial
      property :amount, Integer, :required => true
      property :comment, Text


    end

    class Alias
  include DataMapper::Resource


  belongs_to :user
  has n, :transfers_in, "Transfer"  
  has n, :transfers_out, "Transfer"   

  property :id, String, :key => true, :unique => true

  validates_format_of :id, :with => /[0-9a-z\-]/i

end

对我来说所有这些结果

Started POST "/accounts/2/transfers" for 127.0.0.1

在 2011-06-20 09:16:25 +0400 由 TransfersController#create 作为 HTML 处理 参数：{"utf8"=>"✓", "authenticity_token"=>"token", "转账"=>{"金额"=>"30.3", "alias_from"=>{"id"=>"我的别名"}, "alias_to"=>{"id"=>"他的别名"}, "评论"=>"评论文字"}, “提交”=>“转让”， "account_id"=>"2"} ~ SQL (0.525ms) SELECT "id", "encrypted_pa​​ssword", "remember_created_at", "reset_password_token", "reset_password_sent_at", “失败的尝试”，“解锁令牌”， "locked_at", "sign_in_count", "current_sign_in_at", "last_sign_in_at", "current_sign_in_ip", "last_sign_in_ip", "用户名", “电子邮件”、“姓名”、“国家”来自 “用户” WHERE “id” IN (2) LIMIT 1 ~ SQL (0.495ms) SELECT "id", "name", "currency", "value", "user_id" 从“帐户”WHERE（“user_id”= 2 AND "id" = 2) ORDER BY "id" LIMIT 1 ~ SQL (0.414ms) SELECT "id" FROM "aliases" WHERE "id" = 'My Alias' ORDER BY "id" 限制 1 ~ SQL (0.329ms) SELECT "id" FROM "aliases" WHERE "id" = '他的别名' ORDER BY "id" LIMIT 1 15ms内完成

NoMethodError (undefined method `update' for nil:NilClass):
  app/controllers/transfers_controller.rb:10:in

`创建'

而且我不知道可能是什么问题。有什么建议么？真的很感激。

Answer 1

mu 太短是对的：all 方法返回一个集合，而不是单个对象。相反，您必须使用first:

@account = @owner.accounts.first(:id => :account_id)

或get:

@account = @owner.accounts.get(account_id)

更新，基于评论：

您正在尝试更新别名，但这不是必需的。 transfer 属于 alias_from 和 alias_to。这意味着您的转帐表应该有两列：alias_from_id 和alias_to_id。那是您存储这些值的地方。

您不必使用fields_for。所以，而不是：

<%= trans_form.fields_for :alias_from do |alias_from|%>
  <%= alias_from.label :alias_from %>
  <%= alias_from.collection_select :id, @aliases, :id, :id %> </br>
<%end%>
<%= trans_form.fields_for :alias_to do |alias_to|%>
  <%= alias_to.label :alias_to %>
  <%= alias_to.text_field :id %></br>
<%end%>

你应该能够简单地做到：

<%= trans_form.label :alias_from %>
<%= trans_form.collection_select :alias_from_id, @aliases, :id, :id %> </br>
<%= trans_form.label :alias_to %>
<%= trans_form.text_field :alias_to_id %></br>

你的控制器动作应该是这样的：

def create 
  @owner = current_user
  @account = @owner.accounts.first(:id => params[:account_id])
  @transfer =  @account.transfers.create(params[:transfer])  

  # the rest of your code...
end

更新 2

您可以像这样在模型中设置外键字段的正确名称：

class Transfer
  include DataMapper::Resource    

  belongs_to :account
  belongs_to :alias_from, "Alias", :key => true, :child_key => 'alias_from_id'
  belongs_to :alias_to, "Alias", :key => true, :child_key => 'alias_to_id'

  # Etc...