Step 03: Type-Specific Views¶

In Step 03: Type-Specific Views we had 3 “content types” (SiteFolder, Folder, and Document.) All, however, used the same view and template.

Pyramid traversal though lets you bind a view to a particular content type.

Goals¶

Type-specific views by registering a view against a class

Objectives¶

@view_config which uses the context attribute to associate a particular view with context instances of a particular class
Views and templates which are unique to a particular class (aka type)
Patterns in test writing to handle multiple kinds of contexts

Steps¶

$ cd ../../resources; mkdir step03; cd step03

(Unchanged) Copy the following into step03/application.py:

from wsgiref.simple_server import make_server

from pyramid.config import Configurator

from resources import bootstrap


def main():
    config = Configurator(root_factory=bootstrap)
    config.scan("views")
    app = config.make_wsgi_app()
    return app


if __name__ == '__main__':
    app = main()
    server = make_server(host='0.0.0.0', port=8080, app=app)
    server.serve_forever()

Copy the following into step03/views.py:

from pyramid.view import view_config

from resources import SiteFolder
from resources import Folder
from resources import Document

class ProjectorViews(object):
    def __init__(self, context, request):
        self.context = context
        self.request = request

    @view_config(renderer="templates/site_view.pt",
                 context=SiteFolder)
    def site_view(self):
        return {"children": self.context.values()}

    @view_config(renderer="templates/folder_view.pt",
                 context=Folder)
    def folder_view(self):
        return {"children": self.context.values()}


    @view_config(renderer="templates/document_view.pt",
                 context=Document)
    def document_view(self):
        return {}

(Unchanged) Copy the following into step03/resources.py:

class Folder(dict):
    def __init__(self, name, parent, title):
        self.__name__ = name
        self.__parent__ = parent
        self.title = title


class SiteFolder(Folder):
    pass


class Document(object):
    def __init__(self, name, parent, title):
        self.__name__ = name
        self.__parent__ = parent
        self.title = title


root = SiteFolder('', None, 'Projector Site')

def bootstrap(request):
    # Let's make:
    # /
    #   doc1
    #   doc2
    #   folder1/
    #      doc1
    doc1 = Document('doc1', root, 'Document 01')
    root['doc1'] = doc1
    doc2 = Document('doc2', root, 'Document 02')
    root['doc2'] = doc2
    folder1 = Folder('folder1', root, 'Folder 01')
    root['folder1'] = folder1

    # Only has to be unique in folder
    doc11 = Document('doc1', folder1, 'Document 01')
    folder1['doc1'] = doc11

    return root

Copy the following into step03/templates/document_view.pt:

<div>
    <h2>Document Title: ${context.title}</h2>
</div>

Copy the following into step03/templates/folder_view.pt:

<div>
    <h2>Folder Title: ${context.title}</h2>
    <ul>
        <li tal:repeat="child children">
            <a href="${child.__name__}">${child.title}</a>
        </li>
    </ul>
</div>

Copy the following into step03/templates/site_view.pt:

<div>
    <h2>SiteFolder Title: ${context.title}</h2>
    <ul>
        <li tal:repeat="child children">
            <a href="${child.__name__}">${child.title}</a>
        </li>
    </ul>
</div>

Copy the following into step03/tests.py:

import unittest

from pyramid.testing import DummyRequest
from pyramid.testing import DummyResource

class DummySite(object):
    title = "Dummy Title"
    __name__ = "dummy"
    __parent__ = None

    def values(self):
        return [1,2,3,4,5]
    
class ProjectorViewsUnitTests(unittest.TestCase):

    def _makeOne(self, context, request):
        from views import ProjectorViews
        inst = ProjectorViews(context, request)
        return inst

    def test_site_view(self):
        request = DummyRequest()
        context = DummySite()
        inst = self._makeOne(context, request)
        result = inst.site_view()
        self.assertEqual(len(result['children']), 5)

    def test_folder_view(self):
        request = DummyRequest()
        context = DummySite()
        inst = self._makeOne(context, request)
        result = inst.folder_view()
        self.assertEqual(len(result['children']), 5)

    def test_document_view(self):
        request = DummyRequest()
        context = DummyResource()
        inst = self._makeOne(context, request)
        result = inst.document_view()
        self.assertEqual(result, {})

class ProjectorFunctionalTests(unittest.TestCase):
    def setUp(self):
        from application import main
        app = main()
        from webtest import TestApp
        self.testapp = TestApp(app)

    def test_it(self):
        res = self.testapp.get('/', status=200)
        self.assertTrue('SiteFolder' in res.body)
        res = self.testapp.get('/folder1', status=200)
        self.assertTrue('Folder' in res.body)
        res = self.testapp.get('/doc1', status=200)
        self.assertTrue('Document' in res.body)
        res = self.testapp.get('/doc2', status=200)
        self.assertTrue('Document' in res.body)
        res = self.testapp.get('/folder1/doc1', status=200)
        self.assertTrue('Document' in res.body)

$ nosetests should report running 4 tests.
$ python application.py
Open http://127.0.0.1:8080/ in your browser.

Extra Credit¶

In Zope, interfaces were used to register a view. How do you do register a Pyramid view against instances that support a particular interface?
Can Pyramid accept view registrations against a superclass?
Can you associate a view with multiple classes?

Analysis¶

Our container views now calculate the list of children and pass into the template, letting us navigate to children.

The tests now need more ceremony to mock up some dummy values, then test against them.

Discussion¶

Should you calculate the list of children on the Python side, or access it on the template side by operating on the context?
In what cases are interfaces a better binding mechanism?
Are there times when you want different traversal policies that Pyramid’s default traverser?

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