Nevow Tutorial: part 4

Using the children class attribute

######################################################################
# Run using 'twistd -noy file.tac', then point your browser to
# http://localhost:8080
# A very simple Nevow site.
######################################################################

from twisted.application import service, internet

from nevow               import appserver
from nevow               import rend
from nevow               import loaders
from nevow               import tags as T

class SubPage ( rend.Page ):
    docFactory = loaders.stan (
        T.html [ T.head ( title = 'Sub Page' ),
                 T.body [ T.h1 [ 'This is a Sub Page' ],
                          T.p [ 'I lack much of interest.' ],
                          T.p [ 'You might find ',
                                T.a ( href = '/' ) [ 'this' ],
                                ' more interesting' ],
                          ]
                 ]
        )

class MainPage ( rend.Page ):
    docFactory = loaders.stan (
        T.html [ T.head ( title = 'Main Page' ),
                 T.body [ T.h1 [ 'This is the Main Page' ],
                          T.p [ 'Try going to the pages ',
                                T.a ( href = 'foo' ) [ 'foo' ],
                                ' or ',
                                T.a ( href = 'bar' ) [ 'bar' ],
                                ],
                          T.p [ 'Don't try going ',
                                T.a ( href = 'baz' ) [ 'here' ],
                                ' as it doesn't exist.'
                                ]
                          ]
                 ]
        )

    children = {
        'foo' : SubPage(),
        'bar' : SubPage()
        }

######################################################################
# Nevow Boilerplate
######################################################################

application = service.Application ( 'nevowdemo' )
port        = 8080
res         = MainPage()
site        = appserver.NevowSite ( res )
webService  = internet.TCPServer ( port, site )
webService.setServiceParent ( application )

Note the following:

• Instead of a childFactory() method we have an explicit mapping of child path elements to page objects;
• Two independent child pages, foo and bar have been created. These are persisted in the dictionary; they are not created on demand;
• An attempt to visit a child page that doesn’t have an entry in the children dictionary will fail.

Of course, any page can have children, not just the main page. Try modifying the example above to add another page below the SubPage objects.

Continue on to tutorial-five.