@property<EOL><INDENT>def url(self):<DEDENT>
if self.id:<EOL><INDENT>return '<STR_LIT>' % (<EOL>getConstant('<STR_LIT>'),<EOL>Site.objects.get_current().domain,<EOL>reverse('<STR_LIT>', args=[self.id,]),<EOL>)<EOL><DEDENT>
Because invoice URLs are generally emailed, this
includes the default site URL and the protocol specified in
settings.