ruby on rails - Form for one model in view for another -

i writing simple rails app , have 2 models, location user, have same relationship message model. is, location has many messages, user has many messages, , message belongs user , location. trying add form create new message on location show view. here code:

app/views/locations/show.html.erb:  <h1><%= @locaton.name %></h1> <p><%= @location.location %></p> <p><%= @location.discription %></p> <%= link_to "find different location", crags_path %>  <h2> messages <ul>     <% @location.messages.each |message|%>     </li>         <h3><%=message.user.username%></h3>         <p><%=message.content%></p>     </li>     <% end %> </ul> 

locations controller:

class locationscontroller < applicationcontroller  def index     @locations = location.all end  def show     @location = location.find(params[:id]) end  def new     @location = location.new end  def create     @location = location.new(         name: params[:location][:name],         location: params[:location][:location],         discription: params[:location][:discription])     @location.save     flash.notice = "#{@location.name} created!"     redirect_to location_path(@crag) end  def edit     @location = location.find(params[:id]) end  def update     @location = location.find(params[:id])     @location.update_attributes(params[:location])      flash.notice = "#{@location.name} updated!"      redirect_to crag_path(@location) end  def destroy     @location = location.find(params[:id])     @location.destroy     flash.notice = "#{@location.name} deleted."     redirect_to locations_path end  end 

messagescontroller

class messagescontroller < applicationcontroller  def new     @message = message.new end    def create     @message = current_user.messages.build(                           content: params[:message][:content])     redirect_to crags_path                      end  end 

form partial trying include in location/show.html.erb

<%= form_for(@message) |f| %> <p>     <%= f.label "leave message" %>     <%= f.text_area :content %> </p> <%= f.submit "submit" %> <% end %> 

when try include partial following error

undefined method `model_name' nilclass:class 

and assume form trying communicate locations controller since in locations view, , since cant find instance @message in locations controller, doesn't know do. trying figure out how include form messages controller in view locations. if create view new_message_path works fine, again, guessing because functioning within message views referes messages controller.

i wondering if there way creat message linked both current_user , location form (or when figure out last problem. message object has location_id attribute, how use page on (with url /locations/location_id) link message location? thanks!

firstly, you'll need set @message variable new message in controller:

# locations_controller.rb def show   @location = location.find(params[:id])   @message = @location.messages.build(user_id: current_user.id) end 

using @location.messages.build automatically populate location_id @location.id new message, , we're setting user_id here too.

with in place, should able build form in page (although might need add hidden fields store user_id , location_id @message).

with done, can trim down messages_controller too. unless want have additional page create new message not tied location, can rid of new action (and route). can simplify create action to:

# messages_controller.rb def create   @message = message.new(params[:message])   if @message.save     # whatever want on successful save, example:     flash[:success] = "message created."     redirect_to location_path(@message.location_id)   else     # whatever want if saving fails   end end