_error_messages does not work for forms - ruby-on-rails

Question

I am working on a project that a user can create a post and others can send posts about that topic.My resources file is :
resources :users
resources :sessions, only: [:new, :create, :destroy]
resources :topics , only: [ :show, :create, :destroy] do
resources :posts, only: [:create, :new]
My topics_form.html.erb:
<%= form_for(#topic) do |f| %>
<%= render 'shared/error_messages', object: f.object %>
<div class="field">
<%= f.text_area :title, placeholder: "yeni başlık girin..." %>
</div>
<%= f.submit "Gönder", class: "btn btn-large btn-primary" %>
<% end %>
my create action is :
def create
#topic = current_user.topics.build(params[:topic])
if #topic.save
flash[:success] = "Konu oluşturuldu!"
redirect_to root_path
else
render 'static_pages/home'
end
end
My posts_form.html.erb is :
<%= form_for [#topic, #post] do |f| %>
<%= render 'shared/error_messages', object: f.object %>
<div class="field">
<%= f.text_area :content, placeholder: "yorumunuzu girin..." %>
</div>
<%= f.submit "Gönder", class: "btn btn-large btn-primary" %>
<% end %>
my post_controller create action is :
def create
#topic= Topic.find(params[:topic_id])
#post = #topic.posts.build(params[:post])
#post.user = current_user
#post.topic_id = #topic.id
if #post.save
flash[:success] = "Yorum oluşturuldu!"
redirect_to topic_path(#topic)
else
render 'static_pages/home'
end
end
This is my error_messages.html.erb:
<% if object.errors.any? %>
<div id="error_explanation">
<div class="alert alert-error">
The form contains <%= pluralize(object.errors.count, "error") %>.
</div>
<ul>
<% object.errors.full_messages.each do |msg| %>
<li>* <%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
If I test the empty post and empty topic. I get this error :
undefined method `each' for nil:NilClass
Extracted source (around line #2):
1:
2: <% #topics.each do |topic|%>
3: <li><%=link_to topic.title, topic_path(topic) %></li>
4:
5: <%= will_paginate #topics %>
My static_pages_controller.rb :
def home
if signed_in?
#topic = current_user.topics.build if signed_in?
end
#topics = Topic.paginate :page => params[:page], :per_page => 20
end
and my home.html.erb:
<% if signed_in? %>
<div class="row">
<%= render 'shared/user_info' %>
<%= render 'shared/topic_form' %>
<ol class="topics-signedin">
<%= render 'shared/topics' %>
</ol>
Why does not errors does not show ?

Answer 1

You are missing #topics in your 'create' action. Yes, it gets set in your 'home', which rendered the form, but on submission, it passed to 'create', which then has to load the variables again, and in your case, there is no #topics set when it goes to render 'static_pages/home'. You need..
...
if #post.save
flash[:success] = "Yorum oluşturuldu!"
redirect_to topic_path(#topic)
else
#topics = Topic.paginate :page => params[:page], :per_page => 20
render 'static_pages/home'
end

Answer 2

You never set #topics, only #topic. So #topics is nil.
And on error you render the static_pages/home, which requires those. You should re-render the new or edit instead.