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from zope.interface import implements
from twisted.python.components import registerAdapter, Adapter
from nevow import inevow
from nevow import loaders
from nevow import rend
from nevow import tags as T
## Let's start from the beginning (apart from the various imports):
## We are provided 2 different classes, Person and Bookmark which contain some information (maybe built from a RDBMS
## or directly from an OODB).
## Then the hard stuff begins (I'm not going to explain extensively how adaptation works since there's not enough room,
## but I'm going to give you just a fast overview of how objects and adapter relate to each other):
## We need 2 different adapters since Person and Bookmark are not directly renderable and need some extra
## transformations. What we do here with PersonView and BookmarkView is to define a class that inherits from
## Adapter and define a rend method.
## What is Adapter? Basically it is a class that accepts an argument in the constructor which is the object that
## needs to be adapted to some other interface. Obviously the adapter will implement the interface we need (ie: inevow.
## IRenderer).
## Why do we need to implement IRenderer? An object that implements IRenderer is an object upon which a rend() method
## can be called safely. Since Nevow rendering pipeline uses rend() to serialize objects to html (remember that html tags
## are objects too in Nevow) we need to implement that interface, which is built-in. The adapters we wrote, directly
## implement IRenderer thus we can use them inside the rendering pipeline. Also each adapter holds a reference to the
## corresponding object in self.original.
## Then 2 interesting lines:
## registerAdapter(PersonView, Person, inevow.IRenderer)
## registerAdapter(BookmarkView, Bookmark, inevow.IRenderer)
## Basically we are registering in Nevow object space, that PersonView and BookmarkView are the adapters for classes/
## objects Person and Bookmark to inevow.IRenderer. What does this mean? It means that when we will call inevow.
## IRenderer() interface [later in the Page class] with an instance of Person or Bookmark as argument we will receive the
## right adapter as a result. Without these 2 lines, Nevow doesn't know anything about the way your objects are adapted
## or referenced by each other.
## Then as usual we are creating a bunch of example objects in a list.
## And, last, but not least, we wrote a Page class that uses stan to render the objects list.
############################################################################
# Define some simple classes for out application data.
class Person:
def __init__(self, firstName, lastName, nickname):
self.firstName = firstName
self.lastName = lastName
self.nickname = nickname
class Bookmark:
def __init__(self, name, url):
self.name = name
self.url = url
class PersonView(Adapter):
"""Render a full view of a Person.
"""
implements(inevow.IRenderer)
def rend(self, data):
attrs = ['firstName', 'lastName', 'nickname']
return T.div(_class="View person")[
T.p['Person'],
T.dl[
[(T.dt[attr], T.dd[getattr(self.original, attr)])
for attr in attrs]
]
]
class BookmarkView(Adapter):
"""Render a full view of a Bookmark.
"""
implements(inevow.IRenderer)
def rend(self, data):
attrs = ['name', 'url']
return T.div(_class="View bookmark")[
T.p['Bookmark'],
T.dl[
[(T.dt[attr], T.dd[getattr(self.original, attr)])
for attr in attrs]
]
]
############################################################################
# Register the rendering adapters. Note, these could easily be defined in
# a text file and registered by name rather than class object.
registerAdapter(PersonView, Person, inevow.IRenderer)
registerAdapter(BookmarkView, Bookmark, inevow.IRenderer)
############################################################################
# Create some data for the application to do something with.
objs = [
Person('Valetino', 'Volonghi', 'dialtone'),
Person('Matt', 'Goodall', 'mg'),
Bookmark('Nevow', 'http://www.nevow.com'),
Person('Somebody', 'Else', 'Nevow2004'),
Bookmark('Twisted', 'http://twistedmatrix.com/'),
Bookmark('Python', 'http://www.python.org'),
]
############################################################################
# PSimple Page that renders objs list
class Page(rend.Page):
addSlash = True
def render_item(self, ctx, data):
return inevow.IRenderer(data)
docFactory = loaders.stan(
T.html[
T.body[
T.ul(data=objs, render=rend.sequence)[
T.li(pattern='item')[render_item]
],
],
]
)
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