3 files changed, 14 insertions, 14 deletions
diff --git a/lib/axlsx/util/constants.rb b/lib/axlsx/util/constants.rb
index af8d9702..5ef3ece1 100644
--- a/lib/axlsx/util/constants.rb
+++ b/lib/axlsx/util/constants.rb
@@ -414,5 +414,15 @@ module Axlsx
   # Numeric recognition
   NUMERIC_REGEX = /\A[+-]?\d+?\Z/.freeze
 
+  # Leading characters that indicate a formula.
+  # See: https://owasp.org/www-community/attacks/CSV_Injection
+  FORMULA_PREFIX = '='
+
+  # Leading characters that indicate an array formula.
+  ARRAY_FORMULA_PREFIX = '{='
+
+  # Trailing character that indicates an array formula.
+  ARRAY_FORMULA_SUFFIX = '}'
+
   BOOLEAN_VALUES = [true, false].freeze
 end
diff --git a/lib/axlsx/workbook/worksheet/cell.rb b/lib/axlsx/workbook/worksheet/cell.rb
index cbf55482..4d1bae63 100644
--- a/lib/axlsx/workbook/worksheet/cell.rb
+++ b/lib/axlsx/workbook/worksheet/cell.rb
@@ -73,16 +73,6 @@ module Axlsx
     CELL_TYPES = [:date, :time, :float, :integer, :richtext,
                   :string, :boolean, :iso_8601, :text].freeze
 
-    # Leading characters that indicate a formula.
-    # See: https://owasp.org/www-community/attacks/CSV_Injection
-    FORMULA_PREFIXES = ['='].freeze
-
-    # Leading characters that indicate an array formula.
-    ARRAY_FORMULA_PREFIXES = ['{='].freeze
-
-    # Trailing character that indicates an array formula.
-    ARRAY_FORMULA_SUFFIX = '}'
-
     # The index of the cellXfs item to be applied to this cell.
     # @return [Integer]
     # @see Axlsx::Styles
@@ -396,14 +386,14 @@ module Axlsx
     def is_formula?
       return false if escape_formulas
 
-      type == :string && @value.to_s.start_with?(*FORMULA_PREFIXES)
+      type == :string && @value.to_s.start_with?(FORMULA_PREFIX)
     end
 
     def is_array_formula?
       return false if escape_formulas
 
       type == :string &&
-        @value.to_s.start_with?(*ARRAY_FORMULA_PREFIXES) &&
+        @value.to_s.start_with?(ARRAY_FORMULA_PREFIX) &&
         @value.to_s.end_with?(ARRAY_FORMULA_SUFFIX)
     end
 
diff --git a/lib/axlsx/workbook/worksheet/cell_serializer.rb b/lib/axlsx/workbook/worksheet/cell_serializer.rb
index 2baa4271..f45d3c73 100644
--- a/lib/axlsx/workbook/worksheet/cell_serializer.rb
+++ b/lib/axlsx/workbook/worksheet/cell_serializer.rb
@@ -90,7 +90,7 @@ module Axlsx
       # @param [String] str The string the serialized content will be appended to.
       # @return [String]
       def formula_serialization(cell, str = +'')
-        str << 't="str"><f>' << cell.clean_value.to_s.sub('=', '') << '</f>'
+        str << 't="str"><f>' << cell.clean_value.to_s.delete_prefix(FORMULA_PREFIX) << '</f>'
         str << '<v>' << cell.formula_value.to_s << '</v>' unless cell.formula_value.nil?
       end
 
@@ -99,7 +99,7 @@ module Axlsx
       # @param [String] str The string the serialized content will be appended to.
       # @return [String]
       def array_formula_serialization(cell, str = +'')
-        str << 't="str">' << '<f t="array" ref="' << cell.r << '">' << cell.clean_value.to_s.sub('{=', '').sub(/}$/, '') << '</f>'
+        str << 't="str">' << '<f t="array" ref="' << cell.r << '">' << cell.clean_value.to_s.delete_prefix(ARRAY_FORMULA_PREFIX).delete_suffix(ARRAY_FORMULA_SUFFIX) << '</f>'
         str << '<v>' << cell.formula_value.to_s << '</v>' unless cell.formula_value.nil?
       end