Implements polymorphic associations (Closes #51)

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Dockerfile, docker-compose and Earthfile
 - Test Ruby 3 + Rails 6 on Travis CI
 - Implements the ReQL `during` command
+- Implements polymorphic associations
 
 ## [0.34.1] - 2021-02-18
 ### Fixed

lib/no_brainer/document/association/belongs_to.rb

@@ -3,7 +3,7 @@ class NoBrainer::Document::Association::BelongsTo
 
   class Metadata
     VALID_OPTIONS = [:primary_key, :foreign_key, :class_name, :foreign_key_store_as,
-                     :index, :validates, :required, :uniq, :unique]
+                     :index, :validates, :required, :uniq, :unique, :polymorphic]
     include NoBrainer::Document::Association::Core::Metadata
     include NoBrainer::Document::Association::EagerLoader::Generic
 
@@ -31,7 +31,11 @@ def primary_key
     end
 
     def target_model
-      get_model_by_name(options[:class_name] || target_name.to_s.camelize)
+      if options[:polymorphic]
+        get_model_by_name(owner_model.send([target_name, :type].join('_')))
+      else
+        get_model_by_name(options[:class_name] || target_name.to_s.camelize)
+      end
     end
 
     def base_criteria
@@ -49,6 +53,15 @@ def hook
 
       owner_model.field(foreign_key, :store_as => options[:foreign_key_store_as], :index => options[:index])
 
+      if options[:polymorphic]
+        type_column_name = [target_name, :type].join('_')
+        id_column_name = [target_name, primary_key].join('_')
+
+        owner_model.field(type_column_name.to_sym, type: String)
+        owner_model.field(id_column_name.to_sym, type: String)
+        owner_model.index([id_column_name.to_sym, type_column_name.to_sym])
+      end
+
       unless options[:validates] == false
         owner_model.validates(target_name, options[:validates]) if options[:validates]
 
@@ -97,6 +110,17 @@ def assign_foreign_key(value)
     @target_container = nil
   end
 
+  def polymorphic_read
+    return target if loaded?
+
+    target_id = owner.read_attribute(foreign_key)
+    target_class = owner.read_attribute([target_name, :type].join('_').to_sym)
+
+    if target_id && target_class
+      preload(target_class.where(primary_key => target_id).first)
+    end
+  end
+
   def read
     return target if loaded?
 
@@ -105,6 +129,12 @@ def read
     end
   end
 
+  def polymorphic_write(target)
+    owner.write_attribute(foreign_key, target.try(primary_key))
+    owner.write_attribute([target_name, :type].join('_').to_sym, target.class.name)
+    preload(target)
+  end
+
   def write(target)
     assert_target_type(target)
     owner.write_attribute(foreign_key, target.try(primary_key))

lib/no_brainer/document/association/core.rb

@@ -33,8 +33,8 @@ def delegate(method_src, method_dst, options={})
 
     def hook
       options.assert_valid_keys(*self.class.const_get(:VALID_OPTIONS))
-      delegate("#{target_name}=", :write)
-      delegate("#{target_name}", :read)
+      delegate("#{target_name}=", "#{'polymorphic_' if options[:polymorphic]}write".to_sym)
+      delegate("#{target_name}", "#{'polymorphic_' if options[:polymorphic]}read".to_sym)
     end
 
     def add_callback_for(what)

lib/no_brainer/document/association/has_many.rb

@@ -2,7 +2,8 @@ class NoBrainer::Document::Association::HasMany
   include NoBrainer::Document::Association::Core
 
   class Metadata
-    VALID_OPTIONS = [:primary_key, :foreign_key, :class_name, :dependent, :scope]
+    VALID_OPTIONS = [:primary_key, :foreign_key, :class_name, :dependent, :scope,
+                     :as]
     include NoBrainer::Document::Association::Core::Metadata
     include NoBrainer::Document::Association::EagerLoader::Generic
 
@@ -58,8 +59,21 @@ def eager_load_target_key; foreign_key; end
   end
 
   def target_criteria
-    @target_criteria ||= base_criteria.where(foreign_key => owner.__send__(primary_key))
-                                      .after_find(set_inverse_proc)
+    @target_criteria ||= begin
+      query_criteria = { foreign_key => owner.__send__(primary_key) }
+
+      if metadata.options[:as]
+        polymorphic_id_foreign_key = [metadata.options[:as], primary_key].join('_')
+        polymorphic_type_foreign_key = [metadata.options[:as], :type].join('_')
+
+        query_criteria = {
+          polymorphic_id_foreign_key => owner.__send__(primary_key),
+          polymorphic_type_foreign_key => owner.class.name
+        }
+      end
+
+      base_criteria.where(query_criteria).after_find(set_inverse_proc)
+    end
   end
 
   def read

spec/integration/associations/belongs_to_polymorphic_spec.rb

@@ -0,0 +1,43 @@
+require 'spec_helper'
+
+describe 'belongs_to polymorphic' do
+  before do
+    load_belongs_to_polymorphic_models
+    NoBrainer.sync_indexes
+  end
+
+  let(:event) { Event.create }
+  let(:restaurant) { Restaurant.create }
+
+  context 'creating a polymorphic model document' do
+    it 'saves the model class as type and model id' do
+      picture = Picture.create(imageable: restaurant)
+
+      expect(picture.imageable_type).to eql(restaurant.class.name)
+      # `imageable__id_` instead of imageable_id since the primary key
+      # has been changed for Rspec, see spec/spec_helper.rb line 32-33.
+      expect(picture.imageable__id_).to eql(restaurant._id_)
+    end
+  end
+
+  context 'accessing a has_one polymorphic model document' do
+    it 'returns the associated document' do
+      logo = Logo.create(imageable: restaurant)
+
+      expect(restaurant.logo).to eql(logo)
+    end
+  end
+
+  context 'accessing a has_many polymorphic model document' do
+    it 'returns the associated documents' do
+      picture1 = Picture.create(imageable: restaurant)
+      picture2 = Picture.create(imageable: restaurant)
+
+      expect(restaurant.pictures.to_a).to eql([picture1, picture2])
+
+      picture3 = Picture.create(imageable: event)
+
+      expect(event.pictures.to_a).to eql([picture3])
+    end
+  end
+end

spec/support/models.rb

@@ -99,5 +99,32 @@ def load_polymorphic_models
     end
   end
 
+  def load_belongs_to_polymorphic_models
+    define_class :Logo do
+      include NoBrainer::Document
+
+      belongs_to :imageable, polymorphic: true
+    end
+
+   define_class :Picture do
+      include NoBrainer::Document
+
+      belongs_to :imageable, polymorphic: true
+    end
+
+    define_class :Event do
+      include NoBrainer::Document
+
+      has_many :pictures, as: :imageable
+    end
+
+    define_class :Restaurant do
+      include NoBrainer::Document
+
+      has_one :logo, as: :imageable
+      has_many :pictures, as: :imageable
+    end
+  end
+
   RSpec.configure { |config| config.include self }
 end