to_param and to_query, what's the difference between those methods?
If you are refering to the Array class which has been extended with the two methods #to_param and #to_query, I can tell you that #to_param calls #to_param calls on all its contained elements and joins them with a slash. In contrast #to_query calls #to_query on all contained elements, prefixes them with the first argument ('key') plus and joins it all with an ampersand.
['hello', 'great', 'world'].to_param # => hello/great/world ['hello', 'great', 'world'].to_query('words') # => words%5B %5D=hello&words%5B%5D=great&words%5B%5D=world
#to_param is used after the question mark in a URI, #to_query after.
Hope it makes things clear. 
No, I meant: "#to_param is used BEFORE the question mark in a URI, #to_query after." Like this: hello/great/world?words%5B%5D=hello&words %5B%5D=great&words%5B%5D=world
to_param returns the id by default (this is used in the url /:controller/:action/:id) whereas to_query takes an argument (the parameter key) object_instance.to_query "o" returns the "o=:id" for using at the end of urls - custom/'non-restful' actions but referencing that object.
Thanks to both for the clarification, I was already guessing that to_query was the correct choice for my scenario, but now I'm much more confidant!
cheers Miguel Regedor
I noticed a funny thing, while doing this. We can not use it with an Hash inside an array because the Hash elements will be spread all over the array thanks to URL query brackets syntax for Arrays(if the array index was specified in this syntax it would work, but I don't think there is way to get to_query doing it I think the best way is to use only Hashes instead).
