10 files changed, 12 insertions, 12 deletions
diff --git a/lib/axlsx/drawing/cat_axis.rb b/lib/axlsx/drawing/cat_axis.rb
index 2f40f29f..d26e3dc9 100644
--- a/lib/axlsx/drawing/cat_axis.rb
+++ b/lib/axlsx/drawing/cat_axis.rb
@@ -42,7 +42,7 @@ module Axlsx
     alias :tickMarkSkip :tick_mark_skip
 
     # regex for validating label offset
-    LBL_OFFSET_REGEX = /0*(([0-9])|([1-9][0-9])|([1-9][0-9][0-9])|1000)/
+    LBL_OFFSET_REGEX = /0*(([0-9])|([1-9][0-9])|([1-9][0-9][0-9])|1000)/.freeze
 
     # @see tick_lbl_skip
     def tick_lbl_skip=(v) Axlsx::validate_unsigned_int(v); @tick_lbl_skip = v; end
diff --git a/lib/axlsx/drawing/line_3D_chart.rb b/lib/axlsx/drawing/line_3D_chart.rb
index f9f9606e..60572785 100644
--- a/lib/axlsx/drawing/line_3D_chart.rb
+++ b/lib/axlsx/drawing/line_3D_chart.rb
@@ -26,7 +26,7 @@ module Axlsx
     alias :gapDepth :gap_depth
 
     # validation regex for gap amount percent
-    GAP_AMOUNT_PERCENT = /0*(([0-9])|([1-9][0-9])|([1-4][0-9][0-9])|500)%/
+    GAP_AMOUNT_PERCENT = /0*(([0-9])|([1-9][0-9])|([1-4][0-9][0-9])|500)%/.freeze
 
     # the category axis
     # @return [Axis]
diff --git a/lib/axlsx/drawing/pic.rb b/lib/axlsx/drawing/pic.rb
index fa08bd83..320a5254 100644
--- a/lib/axlsx/drawing/pic.rb
+++ b/lib/axlsx/drawing/pic.rb
@@ -30,7 +30,7 @@ module Axlsx
     end
 
     # allowed mime types
-    ALLOWED_MIME_TYPES = %w(image/jpeg image/png image/gif)
+    ALLOWED_MIME_TYPES = %w(image/jpeg image/png image/gif).freeze
 
     # The name to use for this picture
     # @return [String]
diff --git a/lib/axlsx/drawing/view_3D.rb b/lib/axlsx/drawing/view_3D.rb
index 9b1b5cb2..9b3489a3 100644
--- a/lib/axlsx/drawing/view_3D.rb
+++ b/lib/axlsx/drawing/view_3D.rb
@@ -18,10 +18,10 @@ module Axlsx
     end
 
     # Validation for hPercent
-    H_PERCENT_REGEX = /0*(([5-9])|([1-9][0-9])|([1-4][0-9][0-9])|500)/
+    H_PERCENT_REGEX = /0*(([5-9])|([1-9][0-9])|([1-4][0-9][0-9])|500)/.freeze
 
     # validation for depthPercent
-    DEPTH_PERCENT_REGEX = /0*(([2-9][0-9])|([1-9][0-9][0-9])|(1[0-9][0-9][0-9])|2000)/
+    DEPTH_PERCENT_REGEX = /0*(([2-9][0-9])|([1-9][0-9][0-9])|(1[0-9][0-9][0-9])|2000)/.freeze
 
     # x rotation for the chart
     # must be between -90 and 90
diff --git a/lib/axlsx/stylesheet/dxf.rb b/lib/axlsx/stylesheet/dxf.rb
index 8c32a75f..2c10443a 100644
--- a/lib/axlsx/stylesheet/dxf.rb
+++ b/lib/axlsx/stylesheet/dxf.rb
@@ -8,7 +8,7 @@ module Axlsx
 
     # The order in which the child elements is put in the XML seems to
     # be important for Excel
-    CHILD_ELEMENTS = [:font, :numFmt, :fill, :alignment, :border, :protection]
+    CHILD_ELEMENTS = [:font, :numFmt, :fill, :alignment, :border, :protection].freeze
     # does not support extList (ExtensionList)
 
     # The cell alignment for this style
diff --git a/lib/axlsx/util/storage.rb b/lib/axlsx/util/storage.rb
index 1e12b2d4..00cd6b3c 100644
--- a/lib/axlsx/util/storage.rb
+++ b/lib/axlsx/util/storage.rb
@@ -35,7 +35,7 @@ module Axlsx
     COLORS = {
       :red => 0,
       :black => 1
-    }
+    }.freeze
 
     # The color of this node in the directory tree. Defaults to black if not specified
     # @return [Integer] color
diff --git a/lib/axlsx/workbook/worksheet/auto_filter/filter_column.rb b/lib/axlsx/workbook/worksheet/auto_filter/filter_column.rb
index 16096a52..e5c3ef77 100644
--- a/lib/axlsx/workbook/worksheet/auto_filter/filter_column.rb
+++ b/lib/axlsx/workbook/worksheet/auto_filter/filter_column.rb
@@ -28,7 +28,7 @@ module Axlsx
     serializable_attributes :col_id, :hidden_button, :show_button
 
     # Allowed filters
-    FILTERS = [:filters] # , :top10, :custom_filters, :dynamic_filters, :color_filters, :icon_filters]
+    FILTERS = [:filters].freeze # , :top10, :custom_filters, :dynamic_filters, :color_filters, :icon_filters]
 
     # Zero-based index indicating the AutoFilter column to which this filter information applies.
     # @return [Integer]
diff --git a/lib/axlsx/workbook/worksheet/auto_filter/filters.rb b/lib/axlsx/workbook/worksheet/auto_filter/filters.rb
index 38bafe85..95e1b885 100644
--- a/lib/axlsx/workbook/worksheet/auto_filter/filters.rb
+++ b/lib/axlsx/workbook/worksheet/auto_filter/filters.rb
@@ -24,7 +24,7 @@ module Axlsx
     serializable_attributes :blank, :calendar_type
 
     # Allowed calendar types
-    CALENDAR_TYPES = %w(gregorian gregorianUs gregorianMeFrench gregorianArabic hijri hebrew taiwan japan thai korea saka gregorianXlitEnglish gregorianXlitFrench none)
+    CALENDAR_TYPES = %w(gregorian gregorianUs gregorianMeFrench gregorianArabic hijri hebrew taiwan japan thai korea saka gregorianXlitEnglish gregorianXlitFrench none).freeze
 
     # Flag indicating whether to filter by blank.
     # @return [Boolean]
@@ -157,7 +157,7 @@ module Axlsx
       serializable_attributes :date_time_grouping, :year, :month, :day, :hour, :minute, :second
 
       # Allowed date time groupings
-      DATE_TIME_GROUPING = %w(year month day hour minute second)
+      DATE_TIME_GROUPING = %w(year month day hour minute second).freeze
 
       # Grouping level
       # This must be one of year, month, day, hour, minute or second.
diff --git a/lib/axlsx/workbook/worksheet/data_bar.rb b/lib/axlsx/workbook/worksheet/data_bar.rb
index 482bd029..db224b5e 100644
--- a/lib/axlsx/workbook/worksheet/data_bar.rb
+++ b/lib/axlsx/workbook/worksheet/data_bar.rb
@@ -38,7 +38,7 @@ module Axlsx
     serializable_attributes :min_length, :max_length, :show_value
 
     # instance values that must be serialized as their own elements - e.g. not attributes.
-    CHILD_ELEMENTS = [:value_objects, :color]
+    CHILD_ELEMENTS = [:value_objects, :color].freeze
 
     # minLength attribute
     # The minimum length of the data bar, as a percentage of the cell width.
diff --git a/lib/axlsx/workbook/worksheet/sheet_view.rb b/lib/axlsx/workbook/worksheet/sheet_view.rb
index 73e7533e..b64920bb 100644
--- a/lib/axlsx/workbook/worksheet/sheet_view.rb
+++ b/lib/axlsx/workbook/worksheet/sheet_view.rb
@@ -50,7 +50,7 @@ module Axlsx
                             :view, :top_left_cell, :color_id, :zoom_scale
 
     # instance values that must be serialized as their own elements - e.g. not attributes.
-    CHILD_ELEMENTS = [:pane, :selections]
+    CHILD_ELEMENTS = [:pane, :selections].freeze
 
     # The pane object for the sheet view
     # @return [Pane]