diff --git a/VERSION b/VERSION
new file mode 100644
index 0000000..54d1a4f
--- /dev/null
+++ b/VERSION
@@ -0,0 +1 @@
+0.13.0
diff --git a/lib/netbox_client_ruby.rb b/lib/netbox_client_ruby.rb
index a93bf0c..28df3dc 100644
--- a/lib/netbox_client_ruby.rb
+++ b/lib/netbox_client_ruby.rb
@@ -68,6 +68,16 @@ module NetboxClientRuby
     setting :ssl_options, default: { verify: true }
   end
 
+  def self.load_collection(collection, method_name, class_name)
+    collection.define_method(method_name) { class_name.new }
+    collection.__send__(:module_function, method_name)
+  end
+
+  def self.load_entity(entity, method_name, class_name)
+    entity.define_method(method_name) { |id| class_name.new id }
+    entity.__send__(:module_function, method_name)
+  end
+
   def self.circuits
     NetboxClientRuby::Circuits
   end
diff --git a/lib/netbox_client_ruby/api/circuits.rb b/lib/netbox_client_ruby/api/circuits.rb
index 652aa15..283c9d0 100644
--- a/lib/netbox_client_ruby/api/circuits.rb
+++ b/lib/netbox_client_ruby/api/circuits.rb
@@ -8,8 +8,7 @@ module Circuits
       circuit_types: CircuitTypes,
       circuit_terminations: CircuitTerminations,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { class_name.new }
-      module_function(method_name)
+      NetboxClientRuby.load_collection(self, method_name, class_name)
     end
 
     {
@@ -18,8 +17,7 @@ module Circuits
       circuit_type: CircuitType,
       circuit_termination: CircuitTermination,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { |id| class_name.new id }
-      module_function(method_name)
+      NetboxClientRuby.load_entity(self, method_name, class_name)
     end
   end
 end
diff --git a/lib/netbox_client_ruby/api/dcim.rb b/lib/netbox_client_ruby/api/dcim.rb
index 9eb2483..3386f50 100644
--- a/lib/netbox_client_ruby/api/dcim.rb
+++ b/lib/netbox_client_ruby/api/dcim.rb
@@ -26,8 +26,7 @@ module DCIM
       sites: Sites,
       virtual_chassis_list: VirtualChassisList,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { class_name.new }
-      module_function(method_name)
+      NetboxClientRuby.load_collection(self, method_name, class_name)
     end
 
     {
@@ -54,8 +53,7 @@ module DCIM
       site: Site,
       virtual_chassis: VirtualChassis,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { |id| class_name.new id }
-      module_function(method_name)
+      NetboxClientRuby.load_entity(self, method_name, class_name)
     end
   end
 end
diff --git a/lib/netbox_client_ruby/api/extras.rb b/lib/netbox_client_ruby/api/extras.rb
index 639acf6..f49a4e6 100644
--- a/lib/netbox_client_ruby/api/extras.rb
+++ b/lib/netbox_client_ruby/api/extras.rb
@@ -7,8 +7,7 @@ module Extras
       journal_entries: JournalEntries,
       tags: Tags,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { class_name.new }
-      module_function(method_name)
+      NetboxClientRuby.load_collection(self, method_name, class_name)
     end
 
     {
@@ -16,8 +15,7 @@ module Extras
       journal_entry: JournalEntry,
       tag: Tag,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { |id| class_name.new id }
-      module_function(method_name)
+      NetboxClientRuby.load_entity(self, method_name, class_name)
     end
   end
 end
diff --git a/lib/netbox_client_ruby/api/ipam.rb b/lib/netbox_client_ruby/api/ipam.rb
index f87bb9e..865667e 100644
--- a/lib/netbox_client_ruby/api/ipam.rb
+++ b/lib/netbox_client_ruby/api/ipam.rb
@@ -14,8 +14,7 @@ module IPAM
       vlan_groups: VlanGroups,
       vrfs: Vrfs,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { class_name.new }
-      module_function(method_name)
+      NetboxClientRuby.load_collection(self, method_name, class_name)
     end
 
     {
@@ -30,8 +29,7 @@ module IPAM
       vlan_group: VlanGroup,
       vrf: Vrf,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { |id| class_name.new id }
-      module_function(method_name)
+      NetboxClientRuby.load_entity(self, method_name, class_name)
     end
   end
 end
diff --git a/lib/netbox_client_ruby/api/secrets.rb b/lib/netbox_client_ruby/api/secrets.rb
index 5941c00..a550192 100644
--- a/lib/netbox_client_ruby/api/secrets.rb
+++ b/lib/netbox_client_ruby/api/secrets.rb
@@ -8,16 +8,14 @@ module Secrets
       generate_rsa_key_pair: RSAKeyPair,
       get_session_key: SessionKey,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { class_name.new }
-      module_function(method_name)
+      NetboxClientRuby.load_collection(self, method_name, class_name)
     end
 
     {
       secret_role: SecretRole,
       secret: Secret,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { |id| class_name.new id }
-      module_function(method_name)
+      NetboxClientRuby.load_entity(self, method_name, class_name)
     end
 
     def session_key=(session_key)
diff --git a/lib/netbox_client_ruby/api/tenancy.rb b/lib/netbox_client_ruby/api/tenancy.rb
index 0b885d9..57182f5 100644
--- a/lib/netbox_client_ruby/api/tenancy.rb
+++ b/lib/netbox_client_ruby/api/tenancy.rb
@@ -8,8 +8,7 @@ module Tenancy
       contacts: Contacts,
       contact_groups: ContactGroups,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { class_name.new }
-      module_function(method_name)
+      NetboxClientRuby.load_collection(self, method_name, class_name)
     end
 
     {
@@ -18,8 +17,7 @@ module Tenancy
       contact: Contact,
       contact_group: ContactGroup,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { |id| class_name.new id }
-      module_function(method_name)
+      NetboxClientRuby.load_entity(self, method_name, class_name)
     end
   end
 end
diff --git a/lib/netbox_client_ruby/api/virtualization.rb b/lib/netbox_client_ruby/api/virtualization.rb
index 9235420..0aeb50c 100644
--- a/lib/netbox_client_ruby/api/virtualization.rb
+++ b/lib/netbox_client_ruby/api/virtualization.rb
@@ -9,8 +9,7 @@ module Virtualization
       virtual_machines: VirtualMachines,
       interfaces: Interfaces,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { class_name.new }
-      module_function(method_name)
+      NetboxClientRuby.load_collection(self, method_name, class_name)
     end
 
     {
@@ -20,8 +19,7 @@ module Virtualization
       virtual_machine: VirtualMachine,
       interface: Interface,
     }.each_pair do |method_name, class_name|
-      define_method(method_name) { |id| class_name.new id }
-      module_function(method_name)
+      NetboxClientRuby.load_entity(self, method_name, class_name)
     end
   end
 end
diff --git a/lib/netbox_client_ruby/entity.rb b/lib/netbox_client_ruby/entity.rb
index fc97369..914a228 100644
--- a/lib/netbox_client_ruby/entity.rb
+++ b/lib/netbox_client_ruby/entity.rb
@@ -21,25 +21,12 @@ module ClassMethods
       #   id 'an_id_field' => 'id_field_in_data'
       #   id an_id_field: 'id_field_in_data', :another_id_field: 'id_field2_in_data'
       #
-      def id(*fields) # rubocop:disable Metrics/AbcSize,Metrics/CyclomaticComplexity,Metrics/MethodLength,Metrics/PerceivedComplexity
+      def id(*fields)
         return @id_fields if @id_fields
 
         raise ArgumentError, "No 'id' was defined, but one is expected." if fields.empty?
 
-        @id_fields = {}
-        if fields.first.is_a?(Hash)
-          fields.first.each { |key, value| @id_fields[key.to_s] = value.to_s }
-        else
-          fields.map(&:to_s).each do |field|
-            field_as_string = field.to_s
-            @id_fields[field_as_string] = field_as_string
-          end
-        end
-
-        @id_fields.each_key do |field|
-          define_method(field) { instance_variable_get :"@#{field}" }
-        end
-
+        @id_fields = load_attributes(fields)
         @id_fields
       end
 
@@ -88,6 +75,8 @@ def object_fields(*fields_to_class_map)
         end
       end
 
+      private
+
       def sanitize_mapping(fields_to_class_map) # rubocop:disable Metrics/MethodLength
         fields_map = {}
         fields_to_class_map.each do |field_definition|
@@ -101,6 +90,25 @@ def sanitize_mapping(fields_to_class_map) # rubocop:disable Metrics/MethodLength
         end
         fields_map
       end
+
+      def load_attributes(fields) # rubocop:disable Metrics/AbcSize,Metrics/MethodLength
+        id_fields = {}
+
+        if fields.first.is_a?(Hash)
+          fields.first.each { |key, value| id_fields[key.to_s] = value.to_s }
+        else
+          fields.map(&:to_s).each do |field|
+            field_as_string = field.to_s
+            id_fields[field_as_string] = field_as_string
+          end
+        end
+
+        id_fields.each_key do |field|
+          define_method(field) { instance_variable_get :"@#{field}" }
+        end
+
+        id_fields
+      end
     end
 
     def initialize(given_values = nil) # rubocop:disable Metrics/MethodLength
diff --git a/lib/netbox_client_ruby/version.rb b/lib/netbox_client_ruby/version.rb
new file mode 100644
index 0000000..9d338d2
--- /dev/null
+++ b/lib/netbox_client_ruby/version.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module NetboxClientRuby
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
+  module VERSION
+    STRING = File.read(File.expand_path('../../VERSION', __dir__)).strip
+  end
+end
diff --git a/netbox-client-ruby.gemspec b/netbox-client-ruby.gemspec
index 31ec3f9..029a846 100644
--- a/netbox-client-ruby.gemspec
+++ b/netbox-client-ruby.gemspec
@@ -1,8 +1,10 @@
 # frozen_string_literal: true
 
+require_relative 'lib/netbox_client_ruby/version'
+
 Gem::Specification.new do |spec|
   spec.name          = 'netbox-client-ruby'
-  spec.version       = `git describe --tags --match="v[0-9]*" --abbrev=0`.strip.delete_prefix("v")
+  spec.version       = NetboxClientRuby::VERSION::STRING
 
   spec.summary       = 'A read/write client for Netbox v2.'
   spec.homepage      = 'https://github.com/ninech/netbox-client-ruby'
@@ -19,9 +21,7 @@ Gem::Specification.new do |spec|
     spec.metadata['bug_tracker_uri']   = 'https://github.com/ninech/netbox-client-ruby/issues'
   end
 
-  spec.files = `git ls-files -z`.split("\x0").reject do |f|
-    f.match(%r{^(test|spec|features)/})
-  end
+  spec.files = Dir['README.md', 'LICENSE.txt', 'VERSION', 'lib/**/*.rb']
 
   spec.required_ruby_version = '>= 2.7.0'