Sunday, August 19, 2007

Active Scaffold

After quite a bit of writing and business related non-programming work, I've got my hands back onto Rails. I'm actually crossing a few boundaries by writing an application to help me manage the invoices and employee payments for Cogent (the accounting system does a great job from a purely financial perspective, but I need something that can reflect our internal policies and procedures, which still makes it sound much grander than it is). I've also made a personal commitment to try to understand more about the gems and plugins that I'm using, which brings me to Active Scaffold.

I've used ActiveScaffold in the past for the administrative part consumer facing applications, but this time around I decided to have a closer look at what I could do with it. It's still an exercise in progress, but I've been very impressed with what I've seen so far. Let's look at three simple things first - ordering columns, changing the format of a column value, and filtering the displayed rows.

You tell a controller us use Active Scaffold for CRUD actions by adding a line to your controller. For example, if I want to use ActiveScaffold to maintain the Sale model object then I could set up a controller like this:

active_scaffold :sale

However, the active_scaffold method also takes an optional block, which you can use to customise the behaviour of the scaffold. In particular, there is a method to set the columns in the list view, that you can use like this:

active_scaffold :sale do |config|
config.list.columns = [:invoice_number, :customer, :amount, :status, :salary_package, :entry]

In this case I've specified that there will be six columns in the list view, in precisely the order specified in the array, where the symbols in the array correspond to accessor methods on the Sale model object.

Changing the format of a column is done outside the scaffold configuration, in a helper method. The :amount column is some amount of money, so it would be nicer to format is as a currency amount. The formatter needs to be named {column_name}_column, and it receives the entire model object as its only parameter, so a method to format the amount column in the Admin::SalesScaffoldController would look like this:

module Admin::SalesScaffoldHelper
def amount_column(sale)

Finally, filtering the displayed rows is so simple that I stumbled across the functionality by accident. In my Sales model, the status attribute is an enumerated value that contains, among other values, 'Open' and 'Closed'. I set up a link to the controller like this
link_to :controller => 'admin/sales_scaffold', :action => 'index', :status => 'Open'

and expected to need to explicitly provide some filtering inside the controller. Instead, it worked before I'd done any coding at all! It turns out that any parameters that correspond to attributes are used to filter the results in the table. You can specify a single parameter, or you can specify multiple parameters, in which case they'll be and'd together.

I'm really impressed with the capabilities of Active Scaffold, and I intend to explore them in more depth for applications where the tabular presentation of Active Scaffold is a good fit, and for providing functionality quickly while a user interface design is refined.