Question

Goal: Produce an Excel document with information from 3 associated models that is similar to that in my HTML table. The to_xls gem requires this as a list of arrays.

https://github.com/splendeo/to_xls

Desired output:

(working for both)      (working for both)    (working in HTML, not in Excel)
territory.branch.name    territory.zip    territory.mailedcounts.maximum(:maileddate)
My Branch                90210            2012-05-01
My Branch                90211            2012-05-03
My Branch                90212            

A Branch has many Territories.
A Territory has many Mailedcounts.

I can bring up the correct data in my view via the built in ActiveRecord methods for show.html.erb

<% for territory in @territories %>
<tr>
  <td><%= territory.branch.name %></td>      
  <td><%= territory.zip %></td>
  <td><%= territory.mailedcounts.maximum(:maileddate) %></td>
</tr>
<% end >

This is what I have correctly exporting so far

class BranchesController < ApplicationController
.
.
.
 def show
  @branch = Branch.find(params[:id])
  @territories = @branch.territories

  respond_to do |format|
    format.html
    format.xls { 
      send_data @territories.to_xls(:columns => [ { :branch => :name }, :zip ] )
    }
 end
end

Which gives me territory.branch.name and territory.zip which both work properly. Starting from territory I can’t figure out how to get at my mailedcounts info though.

Answer 1

This is the solution that did it for me. (After far more hours of trying than it should have taken.)

The trick was to define a class in the Mailedcount model, not the Territory model.

class Mailedcount < ActiveRecord::Base
.
.
.
  belongs_to :branch
  belongs_to :territory

  class << self
    def max_maileddate
      maximum('maileddate')
    end
  end
end

Back to the controller I can now call that method.

class BranchesController < ApplicationController
.
.
.
 def show
  @branch = Branch.find(params[:id])
  @territories = @branch.territories

  respond_to do |format|
  format.html
  format.xls { 
    send_data @territories.to_xls(:columns => [ { :branch => :name }, :zip,
                        { :mailedcounts => :max_maileddate } ] )
  }
    end
  end

I couldn’t get a scope or method to work in the Territory model without essentially reproducing the relationship with another join.