Question

Hi there I have 3 files in rails as follows:
1)Located at “app/controller/listings_controller.rb”

class ListingsController < ApplicationController

  def index   
    #Construct kd Tree in memory
    @tree = Listing.constructKDTree;
    @tree.inspect
  end

2) Located at app/models/listing.rb

require 'kd_tree.rb'
class Listing < ActiveRecord::Base

  def constructKDTree
    @contents = self.all

    @kdTree = KDTree.new(@contents) 

  end

3) Located at app/models/kd_tree.rb

class KDTree

  def initialize (db_listings)
    'Initializing Tree' 

  end

end

Now I’m trying to test the method implementation for constructKDTree so I went to my rails console and tried the following commands:

1.9.2-p290 :001 > @lc = ListingsController.new
 => #<ListingsController:0x00000104f3e288 @_routes=nil, @_action_has_layout=true, @_headers={"Content-Type"=>"text/html"}, @_status=200, @_request=nil, @_response=nil> 

1.9.2-p290 :002 > @lc.index

But I get this error:

NoMethodError: undefined method `constructKDTree' for #<Class:0x00000104b1f760>
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.1/lib/active_record/dynamic_matchers.rb:50:in `method_missing'
from /Users/AM/Documents/RailsWS/cmdLineWS/Businesses/app/controllers/listings_controller.rb:20:in `index'
from (irb):2
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands/console.rb:47:in `start'
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands/console.rb:8:in `start'
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'

What am I doing wrong?

Answer 1

You defined constructKDTree as an instance method on Listing. Thus the method is only available on instances of the class but nit the class itself.

Depending on what you actually want to achieve, you can make the method a class method like it’s done in the following code, or you could create a new instance of the Listing class and call the method on the instance.

class Listing < ActiveRecord::Base
  def self.constructKDTree
    @contents = self.all
    @kdTree = KDTree.new(@contents) 
  end
end

However looking at the code you have there, you probably want to do the latter and create a new instance of the class:

listing = Listing.new
@tree = listing.constructKDTree