public InterfaceExtruder(string objcFileContent)
        {
            content = objcFileContent;
            var input = new AntlrInputStream (content);
            lexer = new ObjCLexer (input);
            tokens = new CommonTokenStream (lexer);
            parser = new ObjCParser (tokens);

            listner = new ObjCListnerImpl ();
            walker = new ParseTreeWalker ();
        }

        public override void ExitInstance_method_definition(ObjCParser.Instance_method_definitionContext context)
        {
            var sb = new StringBuilder ();
            sb.Append ('-');
            ObjCParser.Method_definitionContext md = context.method_definition();
            ObjCParser.Method_typeContext method_typeContext = md.method_type ();

            sb.Append (method_typeContext != null ? method_typeContext.GetText () : string.Empty);
            string selector = md.method_selector ().GetText ();
            sb.Append (selector);

            Console.WriteLine (sb);
        }

        public override void ExitProperty_declaration(ObjCParser.Property_declarationContext context)
        {
            var sb = new StringBuilder ();
            sb.Append ("@property");
            sb.Append (' ');

            var attributes = context.property_attributes_declaration ();
            if (attributes != null) {
                sb.Append (attributes.GetText ());
                sb.Append (' ');
            }

            var structDeclaration = context.struct_declaration ();
            sb.Append (structDeclaration.specifier_qualifier_list().GetText());
            sb.Append (' ');
            sb.Append (structDeclaration.struct_declarator_list ().GetText ());

            Console.WriteLine (sb);
        }

 public virtual void ExitVisibility_specification(ObjCParser.Visibility_specificationContext context)
 {
 }

 public virtual void ExitUnary_expression(ObjCParser.Unary_expressionContext context)
 {
 }

 public virtual void ExitType_name(ObjCParser.Type_nameContext context)
 {
     Console.WriteLine ("ExitType_name");
 }

 public virtual void ExitTry_statement(ObjCParser.Try_statementContext context)
 {
 }

 public virtual void ExitTranslation_unit(ObjCParser.Translation_unitContext context)
 {
     Console.WriteLine ("ExitTranslation_unit");
 }

 public virtual void ExitSuperclass_name(ObjCParser.Superclass_nameContext context)
 {
 }

 public virtual void ExitSelector_expression(ObjCParser.Selector_expressionContext context)
 {
 }

 public virtual void ExitSelector(ObjCParser.SelectorContext context)
 {
 }

 public virtual void ExitSelection_statement(ObjCParser.Selection_statementContext context)
 {
 }

 public virtual void ExitRelational_expression(ObjCParser.Relational_expressionContext context)
 {
 }

 public virtual void EnterClass_list(ObjCParser.Class_listContext context)
 {
 }

 public virtual void ExitReceiver(ObjCParser.ReceiverContext context)
 {
 }

 public virtual void ExitStruct_declarator_list(ObjCParser.Struct_declarator_listContext context)
 {
 }

 public virtual void ExitStruct_or_union_specifier(ObjCParser.Struct_or_union_specifierContext context)
 {
 }

 public virtual void ExitSelector_name(ObjCParser.Selector_nameContext context)
 {
 }

 public virtual void ExitSynchronized_statement(ObjCParser.Synchronized_statementContext context)
 {
 }

 public virtual void ExitShift_expression(ObjCParser.Shift_expressionContext context)
 {
 }