On Fri, 2010-12-03 at 17:33 -0800, Seth wrote:
> I've been a TurboGears user for most of my projects but have just been
> hired to start a new Pyramid project. Naturally, I'm interested in the
> traversal approach to views and routes, but am having trouble figuring
> out from the documentation exactly how traversal would work when
> spanning across multiple view classes/modules.
>
>
> Let's look at this typical TurboGears setup, for example (loosely
> adapted to Pyramid):
>
> --> The main root factory (myapp/views/root.py): <--
> from myapp.views.admin.root import AdminRootView
>
> class RootView(object):
> def __init__(self, request):
> self.request = request
>
> admin = AdminRootView
>
> @view_config(renderer='string')
> def index(self):
> return 'index'
>
>
> --> The admin root (myapp/views/admin/root.py): <--
> class AdminRootView(object):
> def __init__(self, request):
> self.request = request
>
>
> @view_config(renderer='string')
> def index(self):
> return 'admin index'
>
> @view_config(name='hello', renderer='string')
> def hello(self):
> return 'admin hello'
>
>
>
> Of course, in a TurboGears-style setup, this would expose views for
> example.com, example.com/admin/, and example.com/admin/hello. However,
> in Pyramid the views for the "sub-views" (/admin/*) don't seem to be
> able to be found. I have succeeded in making this approach work by
> using a "hybrid" setup (using add_route in the config and a
> "route_name" parameter in the view_config), but I can't help but think
> that there's got to be an easier way to do this and I'm just missing
> something.
>
>
> So, is this not really the intended use for traversal? The examples I
> found in the docs about classed-based traversal only go 1-layer deep
> (a Root class). I couldn't seem to land on anything solid explaining a
> larger app setup with views in their own subdirectory and hierarchical
> parent/child classes as separately traversed views. Am I making things
> too verbose, or am I just missing a piece of the puzzle?
Pyramid traversal and TurboGears object dispatch work very differently.
In Pyramid, the graph of objects traversed isnt consulted for view
logic. Instead, the graph is a graph of "model" objects. "Traversal"
is the act of finding a "context". When a context is found, traversal
has done its job. Subsequently a view is looked up based on that
context and data in the request.
An analogue of your above might look like so in Pyramid:
#--> The main root factory (myapp/views/root.py): <--
from pyramid.view import view_config
from pyramid.configuration import Configurator
from paste.httpserver import serve
class AdminModel(object):
pass
class RootView(object):
def __init__(self, request):
self.request = request
@view_config(renderer='string')
def __call__(self):
return 'index'
#--> The admin root (myapp/views/admin/root.py): <--
class AdminRootView(object):
def __init__(self, request):
self.request = request
@view_config(renderer='string', context=AdminModel)
def __call__(self):
return 'admin index'
@view_config(name='hello', renderer='string', context=AdminModel)
def hello(self):
return 'admin hello'
root = {'admin':AdminModel()}
if __name__ == '__main__':
config = Configurator(root_factory = lambda x: root)
config.scan()
app = config.make_wsgi_app()
serve(app)
The root object represents the root of the graph being traversed. The
AdminModel object is present in the graph under the root as the key
"admin".
When traversal traverses "/", the context is the root. Since every
other view is registered for a more specific context, the Root View is
used.
http://localhost:8080/ -> 'index'
When traversal traverses "/admin", the context is the "admin"
AdminModel. Only the views registered for this context will be
considered viable. Since the "view name" is "", the view registered as
"__call__" (no name= argument) on the AdminRootView object will be used:
http://localhost:8080/admin -> 'admin index'
When traversal traverses "/admin/hello", the context is the "admin"
AdminModel. Since the view name is "hello", the view registered as
name="hello" (the hello method of the AdminRootView) will be used.
http://localhost:8080/admin/hello -> 'admin hello'
For more info, see the Traversal chapter in the Pyramid docs:
http://docs.pylonshq.com/pyramid/dev/narr/traversal.html
- C
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