refactor: extracts Subject from Subjects

umich_catalog_indexing/lib/common/subjects.rb

@@ -7,6 +7,7 @@ class Subjects
   end
 end
 
+require_relative "subjects/subject"
 require_relative "subjects/lc_subject"
 require_relative "subjects/non_lc_subject"
 require_relative "subjects/normalize"
@@ -38,32 +39,12 @@ class Subjects
 
     REMEDIATOR = Remediator.new
 
-    class << self
-      def subject_field?(field)
-        SUBJECT_FIELDS.include?(field.tag)
-      end
-
-      # Delegate LC determination to the class itself.
-      def lc_subject_field?(field)
-        LCSubject.lc_subject_field?(field)
-      end
-
-      # Pass off a new subject to the appropriate class
-      def for(field)
-        if lc_subject_field?(field)
-          LCSubject.from_field(field)
-        else
-          NonLCSubject.new(field)
-        end
-      end
-    end
-
     def initialize(record)
       @record = record
     end
 
     def subject_fields
-      sfields = @record.select { |field| self.class.subject_field?(field) }
+      sfields = @record.select { |field| Subject.subject_field?(field) }
       sfields + sfields.flat_map { |field| _linked_fields_for(field) }.compact
     end
 
@@ -72,7 +53,7 @@ def subject_fields
     # @return [Array<MARC::DataField>] A (possibly empty) array of LC subject fields and their
     # linked counterparts, if any
     def lc_subject_fields
-      sfields = @record.select { |field| self.class.lc_subject_field?(field) }
+      sfields = @record.select { |field| Subject.lc_subject_field?(field) }
       sfields + sfields.flat_map { |field| _linked_fields_for(field) }.compact
     end
 

umich_catalog_indexing/lib/common/subjects/subject.rb

@@ -1,6 +1,25 @@
 module Common
   class Subjects
-    class Subject
+    module Subject
+      class << self
+        def subject_field?(field)
+          SUBJECT_FIELDS.include?(field.tag)
+        end
+
+        # Delegate LC determination to the class itself.
+        def lc_subject_field?(field)
+          LCSubject.lc_subject_field?(field)
+        end
+
+        # Pass off a new subject to the appropriate class
+        def new(field)
+          if lc_subject_field?(field)
+            LCSubject.from_field(field)
+          else
+            NonLCSubject.new(field)
+          end
+        end
+      end
     end
   end
 end

umich_catalog_indexing/lib/traject/macros/common/subject.rb

@@ -10,31 +10,31 @@ def lcsh_subjects
       ->(record, accumulator, context) do
         # subject_fields = Common::Subject.lc_subject_fields(record)
         subject_fields = context.clipboard[:subject].lc_subject_fields
-        subjects = subject_fields.map { |f| Common::Subjects.for(f) }
+        subjects = subject_fields.map { |f| Common::Subjects::Subject.new(f) }
         accumulator.replace subjects.map { |s| s.subject_string(" -- ") }
       end
     end
 
     def remediated_lcsh_subjects
       ->(record, accumulator, context) do
         subject_fields = context.clipboard[:subject].remediated_lc_subject_fields
-        subjects = subject_fields.map { |f| Common::Subjects.for(f) }
+        subjects = subject_fields.map { |f| Common::Subjects::Subject.new(f) }
         accumulator.replace subjects.map { |s| s.subject_string(" -- ") }
       end
     end
 
     def non_lcsh_subjects
       ->(record, accumulator, context) do
         subject_fields = context.clipboard[:subject].non_lc_subject_fields
-        subjects = subject_fields.map { |f| Common::Subjects.for(f) }
+        subjects = subject_fields.map { |f| Common::Subjects::Subject.new(f) }
         accumulator.replace subjects.map { |s| s.subject_string(" -- ") }
       end
     end
 
     def subject_browse_subjects
       ->(record, accumulator, context) do
         subject_fields = context.clipboard[:subject].subject_browse_fields
-        subjects = subject_fields.map { |f| Common::Subjects.for(f) }
+        subjects = subject_fields.map { |f| Common::Subjects::Subject.new(f) }
         accumulator.replace subjects.map { |s| s.subject_string }
       end
     end

umich_catalog_indexing/spec/common/subjects/non_lc_subject_spec.rb

@@ -8,7 +8,7 @@
       ["c", "c"])
   end
   subject do
-    Common::Subjects.for(non_lc_subject_field)
+    Common::Subjects::Subject.new(non_lc_subject_field)
   end
   context "lc_subject_field?" do
     it "is false" do

umich_catalog_indexing/spec/common/subjects/subject_spec.rb

@@ -0,0 +1,37 @@
+require "common/subjects"
+RSpec.describe Common::Subjects::Subject do
+  def get_record(path)
+    MARC::XMLReader.new(path).first
+  end
+  let(:record) do
+    get_record("./spec/fixtures/unauthorized_immigrants.xml")
+  end
+  let(:subject_fields) do
+    Common::Subjects.new(record).subject_fields
+  end
+  let(:lc_subject_field) do
+    subject_fields.first
+  end
+  let(:non_lc_subject_field) do
+    subject_fields[2]
+  end
+
+  context ".subject_field?" do
+    it "returns true for appropriate subject field" do
+      expect(described_class.subject_field?(lc_subject_field)).to eq(true)
+    end
+    it "returns false for field with incorrect tag" do
+      not_subject = instance_double(MARC::DataField, tag: "800")
+      expect(described_class.subject_field?(not_subject)).to eq(false)
+    end
+  end
+
+  context ".new" do
+    it "returns an object that knows it's an LCSubject" do
+      expect(described_class.new(lc_subject_field).lc_subject_field?).to eq(true)
+    end
+    it "returns an object that knows it's an Non LCSubject" do
+      expect(described_class.new(non_lc_subject_field).lc_subject_field?).to eq(false)
+    end
+  end
+end