How can I refactor these common controller methods? - ruby-on-rails

Question

I have a few controller methods that are extremely similar and I was wondering what the best way to refactor them would be. First thing that comes to mind would be somehow passing in two blocks to a helper method, but I'm not sure how to do that either.
def action_a
if #last_updated.nil?
#variable_a = #stuff_a
else
#variable_a = (#stuff_a.select{ |item| item.updated_at > #last_updated }
end
end
def action_b
if #last_updated.nil?
#variable_b = #stuff_b.some_method
else
#variable_b = #stuff_b.some_method.select{ |stuff| item.updated_at > #last_updated }
end
end
It just seems like I'm constantly checking if #last_updated is nil (I set the #last_updated instance variable in a before_filter. If I could somehow pass the stuff inside the if as a block and the stuff in the else as another block, then I could remove the if #last_updated.nil? duplication?
What is the best way of accomplishing this for many methods?
Update
Where I specify #stuff_a and #stuff_b, they are always returning an array (since I use .select).

Answer 1

Take a look at this. It's DRYer and should yield identical results.
def action_a
do_the_processing :"#variable_a", #stuff_a
end
def action_b
do_the_processing :"#variable_b", #stuff_b.some_method
end
private
def do_the_processing var_name, collection
if #last_updated.nil?
instance_variable_set var_name, collection
else
instance_variable_set var_name, collection.select{ |item| item.updated_at > #last_updated }
end
end
Update
And here's the two blocks approach (just for fun) (uses 1.9's stabby lambda syntax)
def action_a
check_last_updated is_nil: -> { #variable_a = #stuff_a },
is_not_nil: -> { #variable_a = (#stuff_a.select{ |item| item.updated_at > #last_updated } }
end
def action_b
check_last_updated is_nil: -> { #variable_b = #stuff_b.some_method },
is_not_nil: -> { #variable_b = #stuff_b.some_method.select{ |stuff| item.updated_at > #last_updated } }
end
private
def check_last_updated blocks = {}
if #last_updated.nil?
blocks[:is_nil].try(:call)
else
blocks[:is_not_nil].try(:call)
end
end

Answer 2

You need to extract your condition in a separate def block and use it later on:
def select_updates a
#last_updated.nil? ? a : a.select{ |item| item.updated_at > #last_updated }
end
def action_a; #variable_a = select_updates(#stuff_a) end
def action_b; #variable_b = select_updates(#stuff_b.some_method) end

Answer 3

AS I can see, you could do the followings
have two scope for each
Ex:
class Stuff < ActiveRecord::Base
scope :updated_at, lambda {|updated_date|
{:conditions => "updated_at > #{updated_date}"}
}
end
class Item < ActiveRecord::Base
scope :updated_at, lambda {|updated_date|
{:conditions => "updated_at > #{updated_date}"}
}
end
in your controller do this
def action_a
#variable_a = update_method(#stuff_a)
end
def action_b
#variable_b = update_method(#stuff_b)
end
private
def update_method(obj)
result = nil
if #last_updated.nil?
result = obj.some_method
else
result = obj.some_method.updated_at(#last_updated)
end
result
end
HTH