If I understand correctly you have records in the db and wish to
compare them on demand by the user clicking on a link which goes to a
compare controller. In this case I would pass the id values as
parameters of a GET request on the compare controller. It should not
be a POST as it does not cause the data in the db to be changed. The
actual compare operation should be a method of the model whose objects
are being compared of course.
How can you pass array of parameters to GET request?
The same as anything else, eg
if @my_array contains [0,1,2]
<%= link_to 'Compare', :controller => 'compare', :action =>
'do_compare', :ids => @my_array %>
If the values you want to pass come from fields then it just a matter
of setting up the fields correctly. Google should be able to sort you
out, I always have to look it up.
If you are only comparing two records then just pass the ids as two params.
Whichever makes more sense for you is the way to go. I think I would
probably put it in a compare action in the Plans controller.