Added Target and Threshold models

app/models/target.rb

@@ -0,0 +1,14 @@
+class Target < ActiveRecord::Base
+  belongs_to :goal, inverse_of: :targets
+  belongs_to :item, polymorphic: true, inverse_of: :targets
+  has_many :thresholds, as: :registry, inverse_of: :target, dependent: :destroy,
+    validate: true
+
+  validates :thresholds, presence: true
+  accepts_nested_attributes_for :thresholds, allow_destroy: true,
+    reject_if: proc { |attrs| attrs['quantity_id'].blank? && attrs['value'].blank? }
+  # TODO: validate thresholds count according to condition type
+  validates :condition, inclusion: {in: [:<, :<=, :>, :>=, :==]}
+  validates :scope, inclusion: {in: [:day], if: -> { thresholds.first.domain == :diet }}
+  validates :effective_from, presence: {unless: goal?}, absence: {if: goal?}
+end

app/models/threshold.rb

@@ -0,0 +1,6 @@
+class Threshold < QuantityValue
+  belongs_to :target, foreign_key: 'registry_id', foreign_type: 'foreign_type',
+    inverse_of: :thresholds, polymorphic: true, required: true
+
+  validates :value, numericality: true
+end

db/migrate/001_create_schema.rb

@@ -95,7 +95,7 @@ class CreateSchema < ActiveRecord::Migration
 
     create_table :targets do |t|
       t.references :goal
-      t.references :threshold
+      t.references :item, polymorphic: true
       t.string :condition
       t.string :scope
       t.date :effective_from