I am interested in trying out ar-enumerable in a test Rails app I am working on.

When I run the command below, nothing happens. Have I done something not quite right?

RUBY script/plugin install Svn://rubyforge.org/var/svn/ar-enumerable/ar_enumerable/trunk

Is the plug-in available at this time?

Yes, the plugin is available, I just checked it. You have to make sure that you use the correct URL, in particular, it has to start with “svn:” not “Svn:”, i.e.

svn://rubyforge.org/var/svn/ar-enumerable/ar_enumerable/trunk

If you want to use the AR Enumeration in your app and the Rails plugin loading mechanism is not available, you need to do two things: First, make sure that the directory containing ar_enumerable.rb is in the load path (the Ruby global variable $:). Then execute the code in init.rb.

I’ve been using this plugin on a test basis and I like what I see. Another simple question: can we get a gem (for non-rails work) of this app? I think you’d be surprised the amount of people that are looking for something lik this to use with some type of statistical analysis of data outside rails using activerecord.

Thanks,
Drew

Regarding coordinated iteration over two tables, I haven’t thought of this before, and I don’t have a solution handy. Have a look at the standard Ruby Enumerator and Generator libraries, they may help you get what you need.

Be sure to wrap a transaction block around the combined iteration! ActiveRecord Enumerable internally uses a transaction block, but you have to ensure that all iteration/cursor are in the same single transaction.

I gather that Enumerator/Generator use some callcc magic to jump out of and back into a scope. I’m not completely sure that this won’t mess up things in some way.

This seems like it would be very helpful for a data validation suite I’m attempting to write using ActiveRecord. A couple of questions for you:

1. Can I install this plugin outside of the rails framework? I’m currently only using the ActiveRecord gem in my work.

2. Is there support for manually controlling iteration across the objects? For example, during data validation I’d like to manually compare records from two tables (both of which I’d like to access using your plugin, as they are quite large) and then in some case move to the next object in either 1 or both of the data sets. I need to manually control when the next object is yielded and need to iterate across two tables at the same time. If this is not supported, is there a simple way for me to create some type of where_two method which would give me this functionality?

Seems like a great start on a problem with ActiveRecord that has bothered me for a while

-Drew

Person.where(['lastname = ?', 'Smith']).inject(0) do |income, person|
income += person.income
end

Since the *value* of the block is what’s being stored in ‘income’. So the example should look like this:

Person.where(['lastname = ?', 'Smith']).inject(0) do |income, person|
income + person.income
end