Have a look at the source code of ActiveRecord::Base#assign_multiparameter_attributes and following.
Basically, if you have a class-typed attribute (i.e not :string, :integer and so on) where the constructor of the class takes multiple arguments, you can indicate position and type of these arguments in parentheses. In this way something(1i), something(2s), something(3f) are mapped to
Something.new( <fixnum-value-of-param-something(1i)>, <string-value-of-param-something(2s)>, <float-value-of-param-something(3f)>)
So, if you want to use this in a helper method, you just have to make sure that it generates suitably named form elements
<input type="text" name="something(1i)" /> <input type="text" name="something(2s)" /> <input type="text" name="something(3f)" />
HTH, Michael
