A thoughtbot-style Rails application for managing company expenses
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Expense manager

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This is a Ruby-on-Rails application for tracking company expenses. Here are some interesting aspects:

The facade pattern

The dashboard shows users several pieces of loosely related data together. Instead of reaching across many different models from the controller or view, I created a new object to serve as a single interface (or "Facade") to all the data that is displayed in the view. This makes it possible to access data from a complex API while keeping the controller simple and the logic easy to test.

Scalable spreadsheet-like searching and sorting

Users can search and sort large amounts of data with online "spreadsheets". app/models/user_expense_search and app/models/datatable are responsible for returning JSON compatible with the DataTables.js API, while using Sunspot for searching and ordering.

Sunspot auto-indexes expenses after they are saved or deleted. In addition, I added a mixin module to the related User, Department, and JobTitle classes. Whenever a record changes, the module creates a simple background job to reindex their associated expenses.

Date-based SQL joins

Rails is great at joining records by integer foreign keys. But sometimes, other kinds of joins are necessary for a DRY, normalized database design.

When displaying sums of expenses converted into a single currency, the Expense model joins expenses to exchange rates through a combination of currencies and date ranges, rather than through an integer id. See self.sum_in(currency) and self.joins_exchange_rates(currency).

To ensure each expense is joined to exactly one exchange rate, I used Postgres check constraints with daterange data types and the "&&" overlap operator to prevent records with overlapping currencies and date ranges from being created. Since financial data is at stake, I wrote this validation in the database rather than in ActiveRecord, so that it cannot be easily bypassed.

Getting started

expense_manager comes equipped with a self-setup script:

% ./bin/setup

After setting up, you can run the application using foreman:

% foreman start


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The MIT License. See LICENSE.txt