Dumping objects to the browser in Rails 2

Posted by sjs
on Tuesday, May 15

Here’s an easy way to solve a problem that may have nagged you as it did me. Simply using foo.inspect to dump out some object to the browser dumps one long string which is barely useful except for short strings and the like. The ideal output is already available using the PrettyPrint module so we just need to use it.

Unfortunately typing <pre><%= PP.pp(@something, '') %></pre> to quickly debug some possibly large object (or collection) can get old fast so we need a shortcut.

Taking the definition of Object#pp_s from the extensions project it’s trivial to create a helper method to just dump out an object in a reasonable manner.

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def dump(thing)
  s = StringIO.new
  PP.pp(thing, s)
  "<pre>#{s.string}</pre>"
end

Alternatively you could do as the extensions folks do and actually define Object#pp_s so you can use it in your logs or anywhere else you may want to inspect an object. If you do this you probably want to change the dump helper method accordingly in case you decide to change pp_s in the future.

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class Object
  def pp_s
    pps = StringIO.new
    PP.pp(self, pps)
    pps.string
  end
end
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  1. John Nunemaker – June 10, 2007 @ 03:29 PM

    debug in ActionView::Helpers does a to_yaml output of an object in a view. I use that in views and to_yaml by itself in controllers to simple debugging.

  2. sjs – June 10, 2007 @ 11:28 PM

    doh! I read that in the Rails book after writing this post and felt a bit silly. I should’ve thought that Rails would provide something in the first place. Live and learn. :)

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