add comments

app/models/column.rb

@@ -18,8 +18,13 @@ class Column
     @displayable = displayable
   end
 
+  # the id is a String to be used in forms
   def id = h_id.to_json
+
+  # the h_id is a Hash and hold enough information to find the column
+  # in the ColumnType class, aka be able to do the h_id -> column conversion
   def h_id = { procedure_id: @procedure_id, column_id: "#{table}/#{column}" }
+
   def ==(other) = h_id == other.h_id # using h_id instead of id to avoid inversion of keys
 
   def to_json

app/models/concerns/columns_concern.rb

@@ -4,6 +4,10 @@ module ColumnsConcern
   extend ActiveSupport::Concern
 
   included do
+    # we cannot use column.id ( == { procedure_id, column_id }.to_json)
+    # as the order of the keys is not guaranteed
+    # instead, we are using h_id == { procedure_id:, column_id: }
+    # another way to find a column is to look for its label
     def find_column(h_id: nil, label: nil)
       return columns.find { _1.h_id == h_id } if h_id.present?
       return columns.find { _1.label == label } if label.present?