Extract data preparation into private methods

app/mailers/producer_mailer.rb

@@ -5,22 +5,10 @@ class ProducerMailer < Spree::BaseMailer
     @producer = producer
     @coordinator = order_cycle.coordinator
     @order_cycle = order_cycle
+    @line_items = aggregated_line_items_from(@order_cycle, @producer)
 
     subject = "[#{Spree::Config.site_name}] Order cycle report"
 
-    @line_items = Spree::LineItem.
-      joins(:order => :order_cycle, :variant => :product).
-      where('order_cycles.id = ?', order_cycle).
-      where('spree_products.supplier_id = ?', producer).
-      merge(Spree::Order.complete)
-
-    # Arrange the items in a hash to group quantities
-    @line_items = @line_items.inject({}) do |lis, li|
-      lis[li.variant] ||= {line_item: li, quantity: 0}
-      lis[li.variant][:quantity] += li.quantity
-      lis
-    end
-
     mail(to: @producer.email,
          from: from_address,
          subject: subject,
@@ -28,4 +16,27 @@ class ProducerMailer < Spree::BaseMailer
          cc: @coordinator.email)
   end
 
+
+  private
+
+  def aggregated_line_items_from(order_cycle, producer)
+    aggregate_line_items line_items_from(order_cycle, producer)
+  end
+
+  def line_items_from(order_cycle, producer)
+    Spree::LineItem.
+      joins(:order => :order_cycle, :variant => :product).
+      where('order_cycles.id = ?', order_cycle).
+      merge(Spree::Product.in_supplier(producer)).
+      merge(Spree::Order.complete)
+  end
+
+  def aggregate_line_items(line_items)
+    # Arrange the items in a hash to group quantities
+    line_items.inject({}) do |lis, li|
+      lis[li.variant] ||= {line_item: li, quantity: 0}
+      lis[li.variant][:quantity] += li.quantity
+      lis
+    end
+  end
 end