Question

In my Rails 2 application, a method will receive an arbitrary result set from a find operation, where only a subset of the potential columns will have been returned.

How can I determine, from the resultant objects only, which columns were selected in the find query?

columns won’t help, as that returns all the columns in the table…

Answer 1

You can determine these by using the attribute_names method on any object from the result set.

collection = Model.all(:select=>['col1', 'col2'])

collection.first.attribute_names
#=> ['col1', 'col2']

collection.first.atttributes
#=> {'col1' => "FOO", 'col2'=> 'BAR'}