WIP: targets forms

app/models/quantity_value.rb

@@ -5,7 +5,7 @@ class QuantityValue < ActiveRecord::Base
   # to allow for accessing registry item without knowing QuantityValue (subitem)
   # type, e.g. qv.registry.completed_at
   belongs_to :registry, polymorphic: true
-  belongs_to :quantity, required: true
+  belongs_to :quantity, -> { where(domain: DOMAIN) }, required: true
   belongs_to :unit, required: true
 
   # Uniqueness is checked exclusively on the other end of association level.

app/models/target.rb

@@ -1,6 +1,7 @@
 class Target < ActiveRecord::Base
   belongs_to :goal, inverse_of: :targets, required: true
-  belongs_to :quantity, inverse_of: :targets, required: true
+  belongs_to :quantity, -> { where.not(domain: :target) }, inverse_of: :targets,
+    required: true
   belongs_to :item, polymorphic: true, inverse_of: :targets
   has_many :thresholds, -> { joins(:quantity).order(:lft) },
     as: :registry, inverse_of: :target, dependent: :destroy, validate: true

app/models/threshold.rb

@@ -1,4 +1,6 @@
 class Threshold < QuantityValue
+  DOMAIN = :target
+
   # Need to specify polymorphic association so :registry_type gets written (see
   # QuantityValue for explanation why it's needed)
   belongs_to :target, inverse_of: :thresholds, polymorphic: true, required: true,