Rails 2.3.8 named_scope chaining

I have the following nested if statement hairball, I'm wondering if there is a more efficient way of writing this code (less lines of code that doesn't require so many conditionals)

Each of the methods are named_scopes within the model..

box = (params[:b] ? params[:b] : "inbox")
show = (params[:s] ? params[:s] : "all")

if box == "inbox"
  if show == "all"
    @messages = @current_user.received_messages.all  
  elsif show == "unread"
    @messages = @current_user.received_messages.unread.all  
  elsif show == "read"
    @messages = @current_user.received_messages.read.all  
  elsif show == "starred"
    @messages = @current_user.received_messages.starred.all  
  else
    @messages = []
  end
elsif box = "sent"
  @messages = @current_user.sent_messages.all  
else
  @messages = []
end

My thought was that I could use a 'call' type of method for box and show like

@current_user.开发者_Python百科received_messages.call(:box).call(:show).all

maybe..?

UGH, should have spent a bit more time playing around.. its just as i thought, I was just using the wrong method SOLUTION

@current_user.send(box).send(show)

---

You can use the scoped() method in rails 2.3.8 to chain scopes:

main_method = case (params[:s]||"inbox")
when "inbox"
  :received_messages
when "sent"
  :sent_messages
end
# create a scope. Don't execute the scope yet. 
scope = @current_user.send(main_method).scoped({}) if main_method

# now chain the scope if needed
scope = begin
  if ["unread", "read", "starred"].include?(params[:s])
    scope.send(params[:s])
  elsif((params[:s] || "all") == "all")
    scope
  end
end if main_method == :received_messages

@messages = scope.nil? ? [] : scope.all

Reference:

Scoped method source in Rails 2.3.x

Rails casts on Anonymous scopes in 2.3.x

---

Your answer is very close but it fails to convert box values.

box  = params[:b] || 'inbox'
show = params[:s] || 'all'

box_scope = case box
  when 'inbox' then 'received_messages'
  when 'sent'  then 'sent_messages'
end
show_scope = show # no convertion needed at this point, maybe in the future

# If box_scope is nil, don't query
@messages = box_scope.nil? ? [] : @current_user.send(box_scope).send(show_scope)

This assumes you do away with the .all you were using in the original code for all options, which disappeared in your answer.

---

This is what I figured out, I'm not going to mark my own answer as correct unless everyone agrees this is the best - any other ideas?

if params[:b].present? && ["received_messages", "sent_messages"].include?(params[:b])
  box = params[:b]

  if params[:s].present? && ["all", "unread", "starred"].include?(params[:s])
    show = params[:s]
  else
    show = "all"
  end

  @messages = @current_user.send(box).send(show)
else
  @messages = []
end