Question

I have the model Post:

class Post < ActiveRecord::Base
has_one :location, :dependent => :destroy
belongs_to :person
belongs_to :activity

I have the model Locations:

class Location < ActiveRecord::Base
belongs_to :post
validates :address, :presence => true
attr_accessible :address, :latitude, :longitude
geocoded_by :address
after_validation :geocode, :if => :address_changed?

I need to find all Posts which are in 50 miles from given location. I looked for examples but a did not find what I need. I tried to solve the problem in two ways and failed. I am beginner in Rails and uncounted with the problem, I think that It will be useful for other using has_one model.

I tried:

posts_controller.rb

def index
if params[:saddress].present?
  @locations = Location.near(params[:saddress], 50, :order => :distance)
  for location in @locations
    @posts << location.post
  end
else
  @posts = Post.all
end

index.html.erb

 <h1>Events</h1>
 <fieldset>
 <legend>Find event</legend>
 <%= form_tag(posts_path, :method => "get") do %>
   <%= label_tag(:saddress, "Address:") %>
   <%= text_field_tag :saddress, params[:saddress] %> <br/>
   <%= label_tag(:sactivity, "Activity type:") %>
   <%= select_tag :sactivity, options_from_collection_for_select(Activity.all, "id", "name", params[:sactivity]) %>
   <%= submit_tag "Поиск"%>
 <%end%>
 </fieldset>
 <%if @user%>
   <%= link_to "Новое событие", new_post_path %>
 <%end%>
 <table>
 <tr>
 <th>Created</th>
 <th>Author</th>    
 <th>Event</th>
 <th>Address</th>
 <th>Activity type</th>
 </tr>
 <% for post in @posts.sort.each %>
   <%if post%>
     <tr>
     <td><%= post.created_at %></td>
     <td><%= post.person.name %></td>
     <td><%= link_to post.name, post %></td>
     <td><%if post.location%><%= post.location.address %> <%end%></td>
     <td><%= post.activity.name %></td>
     </tr>
   <%end%>
 <%end%>
 </table>

It resulted in error:

NoMethodError in PostsController#index
You have a nil object when you didn’t expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.<<

Please help me what is wrong. Maybe there is some other easy method for this.

Also I tried this one in posts_controller.rb:

if params[:saddress].present?
  @locations = Location.near(params[:saddress], 50, :order => :distance)
  @posts = Post.find(:all, :include => [:location], :conditions => ["locations.id in ?", @locations])
else
  @posts = Post.all
end

In this case I had problem with SQL.

Answer 1

In your PostsController#index method, you need to initialize the @posts variable. to be an array before you can append items to it. If you ommit that (like you did), @posts is going to be implicitly initialized to nil which explains your error. Change your code like this:

def index
  if params[:saddress].present?
  @posts = []
    @locations = Location.near(params[:saddress], 50, :order => :distance)
    for location in @locations
      @posts << location.post
    end
  else
    @posts = Post.all
  end
end

Another (shorter) variant of the above code is

def index
  if params[:saddress].present?
    @locations = Location.near(params[:saddress], 50, :order => :distance)
    @posts = @locations.collect(&:post)
    # ^^ this is the short form of the following equivalent expression:
    # @posts = @locations.collect{ |loc| loc.post }
  else
    @posts = Post.all
  end
end