Fix thread safety issues

closes #3

lib/xrechnung.rb

@@ -270,18 +270,18 @@ def to_xml(indent: 2, target: "")
         xml.cbc :TaxCurrencyCode, tax_currency_code
         xml.cbc :BuyerReference, buyer_reference
 
-        unless members[:invoice_period][:optional] && invoice_period.nil?
+        unless self.class.members[:invoice_period].optional && invoice_period.nil?
           invoice_period&.to_xml(xml)
         end
 
         xml.cac :OrderReference do
           xml.cbc :ID, purchase_order_reference
-          unless members[:sales_order_reference][:optional] && sales_order_reference.nil?
+          unless self.class.members[:sales_order_reference].optional && sales_order_reference.nil?
             xml.cbc :SalesOrderID, sales_order_reference
           end
         end
 
-        unless members[:billing_reference][:optional] && billing_reference.nil?
+        unless self.class.members[:billing_reference].optional && billing_reference.nil?
           xml.cac :BillingReference do
             billing_reference&.to_xml(xml)
           end
@@ -303,7 +303,7 @@ def to_xml(indent: 2, target: "")
           accounting_customer_party&.to_xml(xml)
         end
 
-        unless members[:tax_representative_party][:optional] && tax_representative_party.nil?
+        unless self.class.members[:tax_representative_party].optional && tax_representative_party.nil?
           xml.cac :TaxRepresentativeParty do
             tax_representative_party&.to_xml(xml)
           end

lib/xrechnung/invoice_line.rb

@@ -40,7 +40,7 @@ def to_xml(xml)
         xml.cbc :InvoicedQuantity, invoiced_quantity.amount_to_s, unitCode: invoiced_quantity.unit_code
         xml.cbc :LineExtensionAmount, *line_extension_amount.xml_args
 
-        unless members[:invoice_period][:optional] && invoice_period.nil?
+        unless self.class.members[:invoice_period].optional && invoice_period.nil?
           invoice_period&.to_xml(xml)
         end
         item&.to_xml(xml)

lib/xrechnung/legal_monetary_total.rb

@@ -40,10 +40,10 @@ class LegalMonetaryTotal
 
     # noinspection RubyResolve
     def to_xml(xml)
-      members.each do |member, _options|
-        next if self[member].nil?
+      self.class.members.each_key do |name|
+        next if self[name].nil?
 
-        xml.cbc :"#{member.to_s.split("_").map(&:capitalize).join}", *self[member].xml_args
+        xml.cbc :"#{name.to_s.split("_").map(&:capitalize).join}", *self[name].xml_args
       end
       xml.target!
     end

lib/xrechnung/member_container.rb

@@ -6,63 +6,54 @@ def self.included(base)
     end
 
     def initialize(**kwargs)
-      self.class.after_initialize.each do |block|
-        instance_eval(&block)
+      # initialize default values
+      self.class.members.each do |name, member|
+        self[name] = member.default.dup unless member.default.nil?
       end
 
       kwargs.each do |k, v|
         self[k] = v
       end
     end
 
-    def members
-      self.class.instance_variable_get :@members
-    end
-
     def [](key)
       send(key)
     end
 
     def []=(key, value)
-      send(members[key].fetch(:setter_name), value)
+      send("#{key}=", value)
     end
 
+    Member = Struct.new(:type, :default, :optional, :transform_value, keyword_init: true)
+
     module ClassMethods
+      def members
+        @members
+      end
+
       # @param [String] member_name
       # @param [Array<Class>, Class] type
       # @param [Object] default
       # @param [TrueClass, FalseClass] optional When true, omits tag rather than rendering an empty tag on nil
       # @param [Proc] transform_value A Proc which is called with the input value to perform type conversion.
-      def member(member_name, type: nil, default: nil, optional: false, transform_value: nil)
+      def member(member_name, **kwargs)
         attr_reader member_name
-        setter_name           = :"#{member_name}="
-        @members[member_name] = { optional: optional, setter_name: setter_name }
+        kwargs[:default].freeze
 
-        if default
-          after_initialize do
-            send(setter_name, default)
-          end
-        end
+        setter_name           = :"#{member_name}="
+        member                = Member.new(**kwargs)
+        @members[member_name] = member
 
         define_method setter_name do |in_value|
-          in_value = transform_value.call(in_value) if transform_value
+          in_value = member.transform_value.call(in_value) if member.transform_value
 
-          if type && !in_value.nil? && Array(type).none? { |t| in_value.is_a?(t) }
-            raise ArgumentError, "expected #{type} for :#{member_name}, got: #{in_value.class}"
+          if member.type && !in_value.nil? && Array(member.type).none? { |t| in_value.is_a?(t) }
+            raise ArgumentError, "expected #{member.type} for :#{member_name}, got: #{in_value.class}"
           end
 
           instance_variable_set :"@#{member_name}", in_value
         end
       end
-
-      def after_initialize(&block)
-        @after_initialize_blocks ||= []
-        if block
-          @after_initialize_blocks << block
-        else
-          @after_initialize_blocks
-        end
-      end
     end
   end
 end

spec/xrechnung_spec.rb

@@ -136,4 +136,13 @@
   it "sets defaults" do
     expect(doc.to_xml).to include "<cbc:InvoiceTypeCode>380</cbc:InvoiceTypeCode>"
   end
+
+  it "thread safe initializer" do
+    doc1 = ::Xrechnung::Document.new
+    doc2 = ::Xrechnung::Document.new
+
+    doc1.invoice_lines << Xrechnung::InvoiceLine.new
+
+    expect(doc2.invoice_lines).to be_empty # Fails - doc1 and doc2 have the same invoice lines
+  end
 end