Extract `casted_true`/`casted_false` for `Type::ImmutableString`

The only difference between `Type::ImmutableString` and its subclasses
is the representation of the casted booleans. Prefer extracting
`casted_true`/`casted_false` and override these by subclasses.

1 files changed, 12 insertions, 4 deletions

diff --git a/activemodel/lib/active_model/type/immutable_string.rb b/activemodel/lib/active_model/type/immutable_string.rb
index 58268540e5..c967d428ac 100644
--- a/activemodel/lib/active_model/type/immutable_string.rb
+++ b/activemodel/lib/active_model/type/immutable_string.rb
@@ -8,8 +8,8 @@ module ActiveModel
       def serialize(value)
         case value
         when ::Numeric, ActiveSupport::Duration then value.to_s
-        when true then "t"
-        when false then "f"
+        when true then casted_true
+        when false then casted_false
         else super
         end
       end
@@ -19,12 +19,20 @@ module ActiveModel
         def cast_value(value)
           result = \
             case value
-            when true then "t"
-            when false then "f"
+            when true then casted_true
+            when false then casted_false
             else value.to_s
             end
           result.freeze
         end
+
+        def casted_true
+          "t".freeze
+        end
+
+        def casted_false
+          "f".freeze
+        end
     end
   end
 end