I am presently using a sort_by on my array

=>    buddies = user_buddies.sort_by {|item| item.last_seen_at}

I would like to be able to do the same , based on a variable    
@criteria   set to the item key to be used

@criteria = 'last_seen_at'   @criteria = 'display_name' ......

=>   buddies = user_buddies.sort_by {|item| item.<@criteria> }

what could be the best way to do it ?

Depending upon another variable @reverse_order = true or false, I would 
like to perform or not teh reverse! action

=> buddies = user_buddies.sort_by {|item| item.last_seen_at}.reverse!

I believe it should be

=> buddies =  @reverse_order ? user_buddies.sort_by {|item| 
item.<@criteria> } : user_buddies.sort_by {|item| item.<@criteria> 
}.reverse!

thanks for your enlightment !

joss