destination.rb in activewarehouse-etl-0.5.0

- old
+ new

@@ -1,28 +1,56 @@
 module ETL #:nodoc:
   module Control #:nodoc:
+    # Base class for destinations.
     class Destination
-      attr_reader :control, :configuration, :mapping
-      attr_accessor :buffer_size, :current_row, :unique
+      # Read-only accessor for the ETL::Control::Control instance
+      attr_reader :control
       
+      # Read-only accessor for the configuration Hash
+      attr_reader :configuration
+      
+      # Read-only accessor for the destination mapping Hash
+      attr_reader :mapping
+      
+      # Accessor to the buffer size
+      attr_accessor :buffer_size
+      
+      # Unique flag.
+      attr_accessor :unique
+      
       class << self
+        # Get the destination class for the specified name.
+        # 
+        # For example if name is :database or 'database' then the DatabaseDestination class 
+        # is returned
         def class_for_name(name)
           ETL::Control.const_get("#{name.to_s.classify}Destination")
         end
       end
       
+      # Initialize the destination
+      #
+      # Arguments:
+      # * <tt>control</tt>: The ETL::Control::Control instance
+      # * <tt>configuration</tt>: The configuration Hash
+      # * <tt>mapping</tt>: The mapping Hash
+      #
+      # Options:
+      # * <tt>:buffer_size</tt>: The output buffer size (default 1000 records)
       def initialize(control, configuration, mapping)
         @control = control
         @configuration = configuration
         @mapping = mapping
         @buffer_size = configuration[:buffer_size] ||= 1000
       end
       
+      # Get the current row number
       def current_row
         @current_row ||= 1
       end
       
+      # Write the given row
       def write(row)
         buffer << row
         flush if buffer.length >= buffer_size
       end
       
@@ -34,15 +62,21 @@
       # Abstract method
       def close
         raise NotImplementedError, "close method must be implemented by subclasses"
       end
       
+      def errors
+        @errors ||= []
+      end
+      
       protected
+      # Access the buffer
       def buffer
         @buffer ||= []
       end
       
+      # Access the generators map
       def generators
         @generators ||= {}
       end
       
       # Get the order of elements from the source order
@@ -74,18 +108,25 @@
       # unique option is specified
       def compound_key_constraints
         @compound_key_constraints ||= {}
       end
       
-      # Add any virtual fields to the row
+      # Add any virtual fields to the row. Virtual rows will get their value from one of the following:
+      # * If the mapping is a Class, then an object which implements the next method
+      # * If the mapping is a Symbol, then the XGenerator where X is the classified symbol
+      # * If the mapping is a Proc, then it will be called with the row
+      # * Otherwise the value itself will be assigned to the field
       def add_virtuals!(row)
         if mapping[:virtual]
           mapping[:virtual].each do |key,value|
             # Engine.logger.debug "Mapping virtual #{key}/#{value} for row #{row}"
             case value
+            when Class
+              generator = generators[key] ||= value.new
+              row[key] = generator.next
             when Symbol
-              generators[key] ||= ETL::Generator::Generator.class_for_name(value).new
-              row[key] = generators[key].next
+              generator = generators[key] ||= ETL::Generator::Generator.class_for_name(value).new
+              row[key] = generator.next
             when Proc
               row[key] = value.call(row)
             else
               row[key] = value
             end
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