Grok for Zope 3 developers
Grok: Zope 3 for cavemen
Grok stands on a giant's shoulder. That giant is Zope 3.
Zope 3 is an advanced object oriented web framework. Zope 3 features a large amount of API documentation and aims for reliability. It has a very large automatic test coverage (many thousands of tests). It has a large set of core features, and sports an enormous range of plug-in components.
The Grok developers think Zope 3 is great. Zope 3, unfortunately, also has some problems: its power raises the entry barrier for developers to get up to speed with it. Even after you've learned it, Zope 3's emphasis on explicit configuration and specification of interfaces can slow down development.
Grok aims to remedy these problems. Grok aims to make Zope 3 easier to learn, and more agile to work with, while retaining the power of Zope 3.
Grok appeals to the caveman or woman in all of us. Cavemen, like us programmers, want powerful and flexible tools. Cavemen are great at tools after all; they invented the whole concept of them. But cavemen, and we, also want our tools to be simple and effective.
Cavemen want tools like clubs: a club is powerful, flexible (you can bash in anything, mash potatoes too) and also simple and effective. Zope 3 is already powerful and flexible. Grok aims to make it simpler and more effective, for beginners and experienced developers alike. Grok: now even cavemen can use Zope 3.
Grok from the Zope 3 perspective
Zope 3 allows you to combine different components in an explicit, flexible way. You can hook up a view to a model, an event handler to an event, and a new API to an existing object. The process of doing this is called configuration. In a technical sense, Grok can be understood as an alternate configuration mechanism for Zope 3.
Zope 3 without Grok uses ZCML for hooking up objects together. ZCML is an XML-based configuration language. ZCML statements are stored in their own file, next to the code. While using ZCML has the benefit of being explicit and flexible, it can also make code harder to read as there are more files to consult in order to understand what is going on.
Grok does away with ZCML. Instead it analyzes your Python code for the use of certain special base classes and directives, and then "groks" it. This grokking process results in the same configuration as it would have if you used the equivalent ZCML. We believe that having all configuration along with your Python code makes the code easier to follow and more fun to develop.
Grok has been designed so that if you organize your code in a certain way, you can even leave out most of the explicit directives in your Python code. This makes code written for Grok look clean and uniform. You still have all the power of explicit configuration available should you need it, however.
During the development of Grok we have taken a careful look at common patterns in Zope 3 code and configuration. Grok aims to make these patterns more easy to use and succinct.
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