Postman is a simple rails plugin that calculates shipping rates based on data from the database. It is meant for cases where the postal service does not have an API for getting the shipping rates.

What Postman does is to get the values from the tables and calculate it out. The values are found in your database tables. You'd have to add the mailing rates into the tables for it to work.

The plugin is very simple. I've included some sql files to help put in the countries and mailing rates(in Singapore). You can use them as a reference.

And here's the original rates:

http://www.singpost.com.sg/quick_services/quicks_03postal_02overseas01.htm

The blog post is here

http://liangzan.net/?p=31

Installation

ruby script/plugin install http://rails-postman.googlecode.com/svn/trunk/postman

Before using it

Generate and apply the migration:

ruby script/generate postman_migration

rake db:migrate

Add values into the tables

• countries

• destinations

• postage_mails

• step_rates

• step_weights

• transit_time

• weight_limit

Definition of the tables

destinations

• the term for the group of countries. Usually postal services group countries up by distance, and set different rates for each zone.

postage_mails

• corresponding rates for the weight

weight_limit

• the maximum weight limit for the rates from postage_mails

step_rates

• the unit rates for additional weight beyond the weight limit

step_weight

• the divisor used to divide up the additional weight

transit_time

• the time needed to ship to the destinations

How to use it

Just call

Postman.postageCalculator("Singapore", 100)

the first argument is the coutry in text, the second argument is the weight in your base unit(which happens to be grams for me) Testing

Create a database called 'plugin_test'

Update the user/password in database.yml

And run 'rake test' from the plugin directory