i created message board application , uses following 3 models work whole thing: forums have many topics, , topics have many posts. posts nested resource of topic, , whenever user chooses "create new topic," 'new' action has nested post start thread. here relative code of that...
topics_controller.rb
class topicscontroller < applicationcontroller load_and_authorize_resource def new @topic = topic.new @post = @topic.posts.build respond_to |format| format.html # new.html.erb format.xml { render :xml => @topic } end end [...] topic.rb
class topic < activerecord::base has_many :posts belongs_to :user, :counter_cache => true belongs_to :forum, :counter_cache => true validates :title, :length => { :maximum => 95 }, :presence => { :message => "you need title topic." } accepts_nested_attributes_for :posts end post.rb
class post < activerecord::base belongs_to :user, :counter_cache => true belongs_to :forum, :touch => true, :counter_cache => true belongs_to :topic, :touch => true, :counter_cache => true validates :body, :presence => { :message => "you have not written text in body." } end new.html.erb
<%= form_for(@topic, :url => forum_topics_path) |f| %> <%= f.label :title %><%= f.text_field :title %> <%= fields_for(@post) |cf|%> <%= cf.label :body %><%= cf.text_area :body, :cols=> 108, :rows => 10 %> <% end %> <%= f.submit %> <% end %> anyway, completed , worked fine.
up until now. out of blue no reason can spot whatsoever, whenever select "create new topic" , directed 'new' action on topics, error of "nomethoderror in topics#new: have nil object when didn't expect it! might have expected instance of array. error occurred while evaluating nil.[]"
this makes absolutely no sense looked @ previous versions in git, , there have been no earth shattering changes made code. perhaps updated rails version (3.0.7) or gem responsible, dunno that.
anyway, line it's throwing fit on in html.erb file, <%= fields_for(@post) |cf|%>. uh...it's new it's supposed nil, right? take out, , works. i've tried redefining @post in topic controller post.new, returns same error. in addition, i've googled on subject says @post = @topic.posts.build way go.
so doing wrong in code above? , idea why work previously, not now?
try this, make sure it's f.fields_for , not fields_for.
<%= form_for(@topic, :url => forum_topics_path) |f| %> <%= f.label :title %><%= f.text_field :title %> <%= f.fields_for(@post) |cf|%> <%= cf.label :body %><%= cf.text_area :body, :cols=> 108, :rows => 10 %> <% end %> <%= f.submit %> <% end %> 
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