ActsAsHistoricalParameter

System and models for working with historically changeing parameters.

Installation

You will need to isert the following javascript into your application.js:

jQuery(function() {
  jQuery('.destroy_historical_value').each(function() {
    var cell = jQuery(this);
    cell.children().hide();
    var button = document.createElement("input");
    jQuery(button).attr("type", "submit");
    jQuery(button).val("Remove");
    jQuery(button).addClass("remove_historical_value_button");
    cell.append(button);
  });

  jQuery(".remove_historical_value_button").live("click", function(event) {
    event.preventDefault();
    var row = jQuery(this).closest("tr")
    row.hide();
    row.find("input[type=hidden]").val(1);
  });

  jQuery('.add_historical_value').click(function(event) {
    event.preventDefault();
    var assoc   = jQuery(this).attr('data-association');
    var content = jQuery('#' + assoc + '_fields_template tbody').html();
    var regexp  = new RegExp('new_' + assoc, 'g');
    var new_id  = new Date().getTime();
        
    jQuery('#' + assoc + '_table tbody').append(content.replace(regexp, new_id));    
    return false;
  });
});

This code uses jQuery. Users of prototype could build code that does the same thing.

Example

class IceCream << ActiveRecord::Base
  # Enable a historical parameter price with id 1
  acts_as_historical_parameter :price, 1

  def get_sales_for_period(period_start, period_end)
    # Do some magic to load # of icecreams of this type
    # sold in the given period
  end

  def get_earnings_for_period(period_start, period_end)
    # Use block sumation to calculate
    price_sum do |period_start, period_end, price|
      # Multiply current price by # of icecreams sold
      get_sales_for_period(period_start, period_end) * value
    end
  end
end

# Load income from first ice for year to date.
IceCream.find(1).get_earnings_for_period(Time.zone.now.beginning_of_year, Time.zone.now)

There are helpers to easilly create a form that allows editing of historical parameters for a model. First if you need to create a form with historical editing use the historical_form_for helper instead of a standard form_for. This will setup the correct builder, this means a form for editing the IceCreams from before will look like:

<%= historical_form_for(@ice_cream) do |f| %>
  <!-- Fields for other attributes ... -->
  <%= f.historical_form_for :price %>
  <%= f.new_history_value_button :price %>
<% end %>

Copyright (c) 2010 KeepFocus A/S, released under the MIT license