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Zope HOWTO

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Revision as of 19:04, January 11, 2014 by Oleg (talk | contribs) (zope, merged into tree from progress, experimental not required anymore)
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This page documents how to use Zope with Funtoo Experimental, which currently has good Zope support thanks to Progress Overlay Python integration.

About Zope

Zope is an Open Source application server framework written in Python. It has an interesting history which you should familiarize yourself with before starting Zope development, as it contains several interesting twists and turns.

Zope History

There are two versions of Zope, Zope 2 and Zope 3. One might assume that Zope 3 is the version that people should use for new software development projects by default, but this is not the case. Most Zope-based projects continue to use Zope 2. Zope 3 was an attempt to redesign Zope 2 from scratch, and is completely different from Zope 2, but it was not adopted by the community.

There is also something called Five (named because it is "2 + 3") that backports many of the new features of Zope 3 into the Zope 2 framework. Several projects will use Zope 2 plus Five in order to use some of the newer features in Zope. Five was merged into mainline Zope 2 in early 2010, and first appeared in Zope 2.8.

You can learn more about the history of Zope 2, 3 and Five in the Five README.

To make things even more interesting, work on Zope 4 is underway, and it will be based on 2.13 rather than 3.x. It includes a number of incompatible changes with prior versions.

   Note

This HOWTO targets Zope 2.13, which includes Five. It is typically the version you should be using for new Zope projects.

Zope Resources

Now that you understand what version of Zope you should be targeting (2.13), we can point you towards the correct documentation :)

The Zope 2 Book
This book provides a general introduction to Zope concepts and ZMI. It is a good place to start, but doesn't provide a direct introduction to Zope development. It's recommended that you skim through this book to familiarize yourself with Zope. It generally does not assume much prior knowledge about Web development or Python.
Zope Developer's Guide
This guide will give you a better introduction to Zope development. It assumes you already know Python. Skip chapters 1 and 2 and start in chapter 3, which covers components and interfaces. Chapter 5 covers the creation of your first product.
Five
We're not done yet. There is a bunch of stuff in Zope 2.13 that is not in the official documentation. Namely, the stuff in Five. Check out The Five Manual.
ZTK
ZTK Documentation
ZCA
A Comprehensive Guide to Zope Component Architecture offers a good introduction to the programming concepts of ZCA. We also have a new page on Zope Component Architecture which will help you to understand the big picture of ZCA and why it is useful. ZCML ("Z-camel") is a part of ZCA and was introduced in Zope 3, so typically you will find ZCML documented within Zope 3 documentation and book.
Content Components
Views and Viewlets: This tutorial on viewlets also contains some viewlet-related ZCML examples near the end. The "Content Component way" of developing in Zope seems to be a Zope 3 thing and tied to ZCML. Chapter 13+ of Stephan Richter's Zope 3 Developer's Handbook (book) seems to cover this quite well. You will probably also want to check out Philipp Weitershausen's Web Component Development with Zope 3 (book).
Zope 2 Wiki
Main wiki page for all things related to Zope 2.
docs.zope.org
This is the main site for Zope documentation.

First Steps

First, you will need to emerge Zope: 

# emerge --jobs=10 zope

Zope is now installed.

Project Skeleton

   Note

Zope should be used by a regular user account, not as the root user.

The first step in using Zope is to ensure that you are using a regular user account. Create a new directory called zope_test: 

$ cd
$ mkdir zope_test

Now, enter the directory, and create an "instance", which is a set of files and directories that are used to contain a Zope project: 

$ cd zope_test
$ /usr/lib/zope-2.13/bin/mkzopeinstance

You will see the following output, and will be prompted to answer a few questions: 

Please choose a directory in which you'd like to install
Zope "instance home" files such as database files, configuration
files, etc.

Directory: instance
Please choose a username and password for the initial user.
These will be the credentials you use to initially manage
your new Zope instance.

Username: admin
Password: ****
Verify password: ****

Now, we will start our Zope instance: 

$ cd instance
$ bin/runzope

Now that Zope is running, you can visit localhost:8080 in your Web browser. You will see a nice introductory page to Zope.

If you now go to the localhost:8080/manage URL, you will be prompted to log in. Enter the username and password you specified. You are now logged in to the ZMI (Zope Management Interface.)

You can stop your application by pressing Control-C. In the future, you can start and stop your Zope instance using the following commands: 

$ zopectl start
$ zopectl stop

zopectl start will cause your instance to run in the background rather than consuming a shell console.

First Project

We will create a single very primitive Zope package, consisting of an Interface for a TODO class, and a TODO class.

Create the following files and directories relative to your project root:

  • Create the directory lib/python/example.
  • Create the file lib/python/example/__init__.py by typing touch lib/python/example/__init__.py.
  • Create these files:

etc/package-includes/example-configure.zcml

This file registers the example directory you created in lib/python as a package, so that it is seen by Zope: 

<include package="example" />

lib/python/example/interfaces.py

The following file defines the ITODO interface, and also uses some Zope Schema functions to define what kind of data we expect to store in objects that implement ITODO: 

from zope.interface import Interface
from zope.schema import List, Text, TextLine, Int

class ITODO(Interface):
    name = TextLine(title=u'Name', required=True)
    todo = List(title=u"TODO Items", required=True, value_type=TextLine(title=u'TODO'))
    daysleft = Int(title=u'Days left to complete', required=True)
    description = Text(title=u'Description', required=True)

lib/python/example/TODO.py

Now, we define TODO to be a persistent object, meaning it can be stored in the ZODB. We specify that it implements our previously-defined ITODO interface, and provide reasonable defaults for all values when we create a new TODO object: 

from persistent import Persistent
from zope.interface import implements
from example.interfaces import ITODO

class TODO(Persistent):
    implements(ITODO)
    name = u''
    todo = []
    daysleft = 0
    description = u''

lib/python/example/configure.zcml

Create an empty configure.zcml configuration file: 

<configure xmlns="http://namespaces.zope.org/zope"
     xmlns:five="http://namespaces.zope.org/five"
     xmlns:browser="http://namespaces.zope.org/browser">
</configure>

Debug Mode

We can test our first project by entering debug mode: 

$ bin/zopectl debug
Starting debugger (the name "app" is bound to the top-level Zope object)

Now, let's try creating a new TODO object and writing it out to a ZODB database: 

>>> from ZODB import FileStorage, DB
>>> storage = FileStorage.FileStorage('mydatabase.fs')
>>> db = DB(storage)
>>> connection = db.open()
>>> import transaction
>>> root = connection.root()
>>> from example.TODO import TODO
>>> a = TODO
>>> a.name = u'My TODOs'
>>> a.TODOS = [ u'Do Laundry', u'Wash Dishes' ]
>>> a.daysleft = 1
>>> a.description = u'Things I need to do today.'
>>> root[u'today'] = a
>>> transaction.commit()
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