ruby-on-rails - Rails应用中的AssociationTypeMismatch(对象预期，获得了HashWithIndifferentAccess)

我收到了AssociationTypeMismatch错误，并且不确定在哪里出错。我对Rails很陌生，所以我猜我在犯一些愚蠢的错误。我检查了语法并将其与AssociationTypeMismatch Error on Ruby on Rails app进行了比较

...但是我似乎仍然无法捕捉到错误。

这是我的模特

class User < ActiveRecord::Base
  attr_accessible :email, :full_name, :password, :password_confirmation, :preference
  has_secure_password

  validates_uniqueness_of :email
  validates_presence_of :full_name

  has_one :preference, :dependent => :destroy

  accepts_nested_attributes_for :preference
end

class Preference < ActiveRecord::Base
  attr_accessible :background_fill, :background_position, :layout

  belongs_to :user
end

这是我的控制器：

def new
  @user = User.new
  @user.build_preference
end

def create
  @user = User.new(params[:user])
  if @user.save
    session[:user_id] = @user.id
    redirect_to root_url, notice: "Thanks for signing up!"
  else
    render "new"
  end
end

这是我的看法：

<%= form_for @user do |f| %>
  <% if @user.errors.any? %>
  <div class="error_messages">
    <h2>There's an error!</h2>
    <ul>
      <% @user.errors.full_message.each do |message| %>
        <li><%= message %></li>
      <% end %>
    </ul>
  </div>
  <% end %>
  <%= f.label :full_name %>
  <%= f.text_field :full_name, :class => "target", :placeholder => "Your full name", :maxlength => "55", :autofocus => "autofocus" %>
  <%= f.label :email %>
  <%= f.email_field :email, :class => "target", :placeholder => "[email protected]", :maxlength => "55" %>
  <%= f.label :password %>
  <%= f.password_field :password, :class => "target", :placeholder => "Enter a password", :maxlength => "55" %>
  <%= f.label :password_confirmation, "Confirmation" %>
  <%= f.password_field :password_confirmation, :class => "target", :placeholder => "Enter your password again", :maxlength => "55" %>
  <%= f.fields_for :preference do |builder| %>
    <%= builder.hidden_field :layout, value: params[:layout] %>
    <%= builder.hidden_field :background_fill, value: params[:background_fill] %>
    <%= builder.hidden_field :background_position, value: params[:background_position] %>
  <% end %>
  <%= f.submit "Create an Account", :class => "button cta" %>
<% end %>

而我的参数

{"utf8"=>"✓",
"authenticity_token"=>"[redacted]=",
"user"=>{"full_name"=>"test",
"email"=>"[email protected]",
"password"=>"[FILTERED]",
"password_confirmation"=>"[FILTERED]",
"preference"=>{"layout"=>"layout-3",
"background_fill"=>"restaurant-2",
"background_position"=>"position-center"}},
"commit"=>"Create an Account"}

编辑：
我得到的错误是Preference(#70124732528700) expected, got ActiveSupport::HashWithIndifferentAccess(#70124687315200)。我的理解是@user.build_preference和accepts_nested_attributes_for :preference只能单独工作。

我是否需要根据创建def preferences_attributes=？
http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-fields_for

更新资料
好吧，我想我离这儿越来越近了。在Rails控制台中四处寻找，我认为需要先在UserController中创建Preference.new，然后才能传递哈希值。因为我不确定build_preference到底能做什么，所以我还没有运气。

我尝试在构建首选项上方添加@user.preference = Preference.new并将f.field_for :preference更改为f.field_for @user.preference，但是仍然出现相同的错误。

更新2
对于解决此问题的其他人，答案是将f.field_for :preference更改为f.field_for :preference_attributes。请参见下面的zetetic评论。

最佳答案

它是：

attr_accessible :preference_attributes

并以您的形式：

<%= f.fields_for :preference_attributes do |builder| %>
...