Improved RDF::NTriples::Writer and fixed a regression bug in #format_…

…node.

lib/rdf/ntriples/writer.rb

@@ -12,7 +12,7 @@ class Writer < RDF::Writer
     # @param  [String] text
     # @return [void]
     def write_comment(text)
-      puts "# #{text}"
+      puts "# #{text.chomp}" # TODO: correctly output multi-line comments
     end
 
     ##
@@ -23,44 +23,64 @@ def write_comment(text)
     # @param  [RDF::Value]    object
     # @return [void]
     def write_triple(subject, predicate, object)
-      puts "%s %s %s ." % [subject, predicate, object].map { |value| format_value(value) }
+      puts format_triple(subject, predicate, object)
+    end
+
+    ##
+    # Returns the N-Triples representation of a statement.
+    #
+    # @param  [RDF::Statement] statement
+    # @return [String]
+    def format_statement(statement)
+      format_triple(*statement.to_triple)
+    end
+
+    ##
+    # Returns the N-Triples representation of a triple.
+    #
+    # @param  [RDF::Resource] subject
+    # @param  [RDF::URI]      predicate
+    # @param  [RDF::Value]    object
+    # @return [String]
+    def format_triple(subject, predicate, object)
+      "%s %s %s ." % [subject, predicate, object].map { |value| format_value(value) }
     end
 
     ##
     # Returns the N-Triples representation of a blank node.
     #
-    # @param  [RDF::Node] value
+    # @param  [RDF::Node] node
     # @param  [Hash{Symbol => Object}] options
     # @return [String]
-    def format_node(value, options = {})
+    def format_node(node, options = {})
       "_:%s" % node.id
     end
 
     ##
     # Returns the N-Triples representation of a URI reference.
     #
-    # @param  [RDF::URI] value
+    # @param  [RDF::URI] literal
     # @param  [Hash{Symbol => Object}] options
     # @return [String]
-    def format_uri(value, options = {})
-      "<%s>" % uri_for(value)
+    def format_uri(uri, options = {})
+      "<%s>" % uri_for(uri)
     end
 
     ##
     # Returns the N-Triples representation of a literal.
     #
-    # @param  [RDF::Literal, String, #to_s] value
+    # @param  [RDF::Literal, String, #to_s] literal
     # @param  [Hash{Symbol => Object}] options
     # @return [String]
-    def format_literal(value, options = {})
-      case value
+    def format_literal(literal, options = {})
+      case literal
         when RDF::Literal
-          text = quoted(escaped(value.value))
-          text << "@#{value.language}" if value.language
-          text << "^^<#{uri_for(value.datatype)}>" if value.datatype
+          text = quoted(escaped(literal.value))
+          text << "@#{literal.language}" if literal.has_language?
+          text << "^^<#{uri_for(literal.datatype)}>" if literal.has_datatype?
           text
         else
-          quoted(escaped(value.to_s))
+          quoted(escaped(literal.to_s))
       end
     end
   end