ModelAttribute: Add `.classes` method

This allows people to get a list of the classes defined in
`ModelAttribute`. The classes are turned into constant-cased strings.
Not sure if that's useful, but this is how it was described in the
ticket.

Refs #4401

2 files changed, 24 insertions, 0 deletions

diff --git a/lib/model_attribute.rb b/lib/model_attribute.rb
index e74dd1060..53c0b7a46 100644
--- a/lib/model_attribute.rb
+++ b/lib/model_attribute.rb
@@ -9,6 +9,14 @@ class ModelAttribute
     all << new(klass, name, data_type)
   end
 
+  def self.classes
+    all
+      .map(&:klass)
+      .map(&:to_s)
+      .map(&:camelize)
+      .uniq
+  end
+
   def self.methods_by_class(klass)
     all.select do |model_attr|
       model_attr.klass == klass
diff --git a/spec/lib/model_attribute_spec.rb b/spec/lib/model_attribute_spec.rb
index faea0b483..9e10bf40f 100644
--- a/spec/lib/model_attribute_spec.rb
+++ b/spec/lib/model_attribute_spec.rb
@@ -14,6 +14,22 @@ RSpec.describe ModelAttribute do
     end
   end
 
+  describe ".classes" do
+    it "returns the list of classes of ModelAttributes in .all" do
+      ModelAttribute.instance_variable_set(:@__all__, [
+        ModelAttribute.new(:route, :name, :string),
+        ModelAttribute.new(:journey_pattern, :name, :string),
+        ModelAttribute.new(:time_table, :start_date, :date)
+      ])
+
+      expect(ModelAttribute.classes).to match_array([
+        'Route',
+        'JourneyPattern',
+        'TimeTable'
+      ])
+    end
+  end
+
   describe ".methods_by_class" do
     it "returns all ModelAttributes for a given class" do
       ModelAttribute.instance_variable_set(:@__all__, [