nix the string interpolation

thanks Keenan and Jason :)

app/models/mixins/aggregation_mixin/methods.rb

@@ -39,12 +39,11 @@ def all_storages
     end
 
     def aggregate_hardware(from, field, targets = nil)
-      from      = from.to_s.singularize
+      from      = from.to_s.singularize.to_sym
       select    = field == :aggregate_cpu_speed ? "cpu_total_cores, cpu_speed" : field
       targets ||= send("all_#{from}_ids")
       targets   = targets.collect(&:id) unless targets.first.kind_of?(Integer)
-      hdws      = Hardware.where("#{from}_id".to_sym => targets).select(select)
-
+      hdws      = Hardware.where(from => targets).select(select)
       hdws.inject(0) { |t, hdw| t + hdw.send(field).to_i }
     end
 

spec/models/mixins/aggregation_mixin_spec.rb

@@ -112,6 +112,13 @@
     end
   end
 
+  describe "aggregate_hardware" do
+    it "calculates from hosts" do
+      cluster = cluster_2_1_host(hardware_args)
+      expect(cluster.aggregate_hardware("host", :aggregate_cpu_speed)).to eq(cpu_speed * 2)
+    end
+  end
+
   private
 
   def cluster_2_1_host(hardware_args)