Cleanest way to justify plain-text columnized layouts?

In a plain-text .erb template, what method would you suggest I use to produce the most maintainable/readable code for something like this:

ITEM DESCRIPTION                                           QTY       PRICE

Product Name One                                             1      $10.00
Another Product With a Longer Name                           2       $5.00
Yet Another Item                                             1      $30.00

Where each of those rows is (obviously) variable, based on the items that have been purchased.

I could calculate the need开发者_如何学Ced whitespace in a helper method, but is this already a solved problem with a more elegant solution?

Looks like one can actually pass a format attribute to the ERB template to do this. I used this trick recently in a pull request for rumm.

My example follows:

Fist the erb template looks like the following:

 ID                Name
 ==                ====
<% this.each do |flavor| %>
  <%= '%-17s %-7s' % [flavor.id, flavor.name] %> 
<% end %>

This outputs data that looks like this:

ID                Name
==                ====
2                 512MB Standard Instance
3                 1GB Standard Instance
4                 2GB Standard Instance
5                 4GB Standard Instance
6                 8GB Standard Instance
7                 15GB Standard Instance
8                 30GB Standard Instance
performance1-1    1 GB Performance
performance1-2    2 GB Performance
performance1-4    4 GB Performance
performance1-8    8 GB Performance
performance2-120  120 GB Performance
performance2-15   15 GB Performance
performance2-30   30 GB Performance
performance2-60   60 GB Performance
performance2-90   90 GB Performance

Sounds like you need a plain text table generator. The only one I can think of for ruby is this: https://github.com/visionmedia/terminal-table but there may be others if this one doesn't fit your needs.

I ended up just using printf() with padding format options. The terminal table thing looked a bit over-complex for this situation, but useful for more complex requirements, such as displaying tabulated result sets.