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pyramid_extdirect 0.5.0

ExtDirect Implementation for Pyramid

Introduction:

This pyramid plugin provides a router for the ExtDirect Sencha API included in ExtJS .

ExtDirect allows to run server-side callbacks directly through JavaScript without the extra AJAX boilerplate. The typical ExtDirect usage scenario goes like this:

MyApp.SomeClass.fooMethod(foo, bar, function(response) {
    // do cool things with response
});

or even better, if ExtDirect is used in a GridStore:

var usersStore = new Ext.data.Store({
    fields: ['id', 'name', 'title'],
    proxy: {
        type: 'direct',
        directFn: MyApp.Users.loadAll,
        reader: {
            type: 'json',
            rootProperty: 'items'
        }
    }
    // ...
});

Here MyApp is the application namespace, SomeClass or Grids are classes or actions and fooMethod and loadGridData are methods.

Usage example:

The minimum requirement for pyramid_extdirect is to create an ExtDirect API and Router:

from pyramid.config import Configurator
from exampleapp.resources import Root

def main(global_config, **settings):
    """ This function returns a Pyramid WSGI application.
    """
    config = Configurator(root_factory=Root, settings=settings)
    config.add_view('exampleapp.views.my_view',
                    context='exampleapp:resources.Root',
                    renderer='exampleapp:templates/mytemplate.pt')
    config.add_static_view('static', 'exampleapp:static')
    # let pyramid_extdirect create all the needed views automatically
    config.include('pyramid_extdirect')
    # scan your code once to make sure the @extdirect_method decorators
    # are picked up
    config.scan()
    return config.make_wsgi_app()

After this you can decorate arbitrary functions or class methods using @extdirect_method:

@extdirect_method(action='SomeAction')
def do_stuff(a, b, c):
    return a + b + c

Or, if you’d like to group your methods into classes (actions), you can do so by decoration class methods:

The UsersController class could combine all methods for users CRUD operations, the only requirement is that this class accepts request as its first and only constructor argument, this is needed to make sure your methods have access to request at any time:

from pyramid_extdirect import extdirect_method

class UsersController(object):

    __extdirect_settings__ = {
        'default_action_name': 'Users',
        'default_permission': 'view'
    }

    def __init__(self, request):
        self.request = request

    # we don't need to set ``action`` here, because
    # it's already defined via __extdirect_settings__
    @extdirect_method(permission='view', method_name='loadAll')
    def load_all(self, params):
        # params is a simple dict that will contain the
        # paging and sorting options as well as any other
        # extra parameters (defined using proxy.extraParams
        # your store config)
        users = []
        for user in users_db.fetch_all():
            users.append({
                id: obj.id,
                name: obj.name,
                title: obj.title,
                # ...
            })
        return dict(success=True, items=users)

As you can see, the Users#loadAll method doesn’t even know it’s been called through a HTTP request, it’s just a plain old python method which returns a dict. The @extdirect_method(permission='view') decoration adds it to the Users action (also making sure only users with view permission are allowed to run it). We’re returning a dict here simply because the AJAX response sent to the client has to be JSON serializable. By default python JSON marshallers can only encode/decode builtin python primitives. pyramid_extdirect has a small helper though, that checks if an object has a method called json_repr() (which should return a JSON serializable dict/list/string/number/etc.) and if found, this method is used to decode an instance to its JSONable version. You can define a __extdirect_settings__ property in a class to define a default action and permission, so in the example above we could also just use @extdirect_method().

Sometimes you need to use the upload features of ExtDirect. Since uploads cannot be done using AJAX (through JSON-encoded request body) Ext does a little trick by creating a hidden iframe and posting a form within this iframe to the server. However, ExtDirect needs to know in advance, that your code might receive uploads. In pyramid_extdirect decorators this is done by adding a accepts_files parameter to the @extdirect_method decorator:

class Users(object):
    ...
    @extdirect_method(accepts_files=True)
    def upload_avatar(self, uploaded_file):
        # uploaded_file is now a FieldStorage instance

In some situations it is absolutely necessary to access the request object in your functions and you don’t want to create an extra class (where the request would be passed in to the class constructor) – this can be achieved by passing request_as_last_param to the decorator:

from pyramid.security import authenticated_userid

@extdirect_method(action='App', request_as_last_param=True):
def get_current_user(request):
    return authenticated_userid(request)

Igor Stroh, <igor.stroh -at- rulim.de>

 
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