2つのモデルがあります：userとprofile、そしてそれらにデータを入力するために同じフォームを使用したいと思います。
userビューとコントローラー内で作業します。私は列のための作業フォームを持っていuserます。ただし、プロファイルモデルに関しては、ユーザービューからどのようにアクセスできますか？
user.rb：
class User < ActiveRecord::Base
has_one :profile
#....#
end
profile.rb：
class Profile < ActiveRecord::Base
# attr_accessible :title, :body
belongs_to :user
end
users / new.html.erb：
<%= form_for @profile do |f| %>
<% if @profile.errors.any? %>
<div class="error_messages">
<h2>Form is invalid</h2>
<ul>
<% for message in @profile.errors.full_messages %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<%= f.label :height, "My height is: (cm)" %><%= f.select :height, options_for_select(140..220) %><br>
<%= f.submit "Next" %>
<% end %>
これを行うと、次のエラーメッセージが表示されます。
undefined method `model_name' for NilClass:Class
編集：
class ApplicationController < ActionController::Base
protect_from_forgery
private
def current_user
@current_user ||= User.find(session[:user_id]) if session[:user_id]
end
helper_method :current_user
end
nil：NilClassの未定義メソッド`profile'のトレース
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