[Zope3-Users] Re: Intended scope of viewlets?

Fri Oct 6 11:59:23 EDT 2006

Hi Jürgen,

So, just to give a concrete example for my case, I might replace this
(Metal-based):

<body>

<div id="Navigation">
  <div metal:define-slot="navigation">
    Nav tree needs a wee bit of work.
  </div>
</div>

<div id="Content">
  <div metal:define-slot="body">
   Some Content
  </div>
</div>

</body>

with this (viewlet-based):

<body>

<div id="Navigation">
    <span tal:replace="structure provider:my.project.navigation">
      Nav tree needs a wee bit of work.
    </span>
</div>

<div id="Content">
  <span tal:replace="structure provider:my.project.content">
    Some Content
  </span>
</div>

</body>

With seperate viewlet managers for "navigation" and "content", or any
other types of views I would expect to have on this page? Would a
"header" viewlet manager also be sensible, say if I wanted a title
that changed format depending on what type of content was being
viewed?

Finally, are there any best practices for packaging in viewlet-based
templating? I'm currently creating this in my.project.browser.skin.
How about the viewlet manager names, should they be my.project.*,
my.project.browser.*, or something different?

Probably some of these questions aren't relevant to the work you are
doing on viewlets, but I find it helpful to try to follow industry
practices as closely as possible, especially on something I don't have
much experience with, so I am easily able to follow tutorials, and
people who are helping me can more easily understand what I am trying
to do.

Thanks very much for your help so far, I am excited about implementing
viewlets in our upcoming project.

Alec

On 10/5/06, Jürgen Kartnaller <juergen at kartnaller.at> wrote:
> Hi Alec.
>
> Alec Munro wrote:
> > Hi List,
> >
> > I'm just getting up to speed with viewlets, having read a thread here
> > and there in the past about them. I've installed the examples provided
> > on this list, and while I believe I understand how they work, I don't
> > understand in what circumstances they are most useful. The viewlets in
> > the examples are all very small, such as retrieving an formatting a
> > single piece of information about an object. However, from some of the
> > posts to this list, I get the impression they are also being used for
> > more complex items, like navigation menus.
>
> Menus are a perfect example for the use of viewlets.
> Have a look at z3c.menu. This package contains a base implementation for
> menus based on viewlets.
>
> > Is there a recommended scope? Can they be described in a way such as
> > "develop your templates up to point X, then use a viewlet for
> > development of further depth?".
> >
> > In my case, I am developing a new skin for a project, and my
> > experience with metal says to make the entire HTML page a macro with
> > slots for content and navigation. Is there a comparable viewlet-based
> > paradigm?
>
> Yes there is one, see below
>
> >
> > Also, am I correct in stating that when working with viewlets, the
> > only complete HTML page will be the primary skin file, with all
> > viewlets based on snippets of HTML?
>
> Thats exacly what we at Lovely Systems do and it works perfectly :)
>
> We have one base template which is used for all pages. Instead of
> defining slots to be filled by other templates it contains viewlet managers.
> We then provide different view classes to be able to register our
> viewlets for the pages of the application.
> The view classes are empty classes they are just providing the class
> name or if they provide additional functionality they also provide an
> interface.
> It is then possible to register the viewlets for specific pages.
> The most important thing on viewlets is that they are adapters on the
> *context*, the *request*, the *view* and the *manager*.
>
> The viewlet solution is an extremely productive way to implement a
> complex application.
>
> Make sure you read this :
> http://blogs.lovelysystems.com/srichter/2006/09/20/the-skin-browser-and-lovely-systems-new-development-workflow/
>
> Stephan Richter describes here our use of the viewlet concept and our
> development workflow. The most important part was the development of the
> package z3c.viewtemplate. This package makes it possible to separate the
>   development of the HTML page from the implementation of the python
> view class. The package is not yet perfect but gives us what we need
> right now but it needs a better integration into forms and viewlets.
> Expect more in the near future!
>
> In our applications really everything is done using viewlets, there is
> no single use of fill-slot in the hole application!
>
> >
> > My questions are fairly broad-ranging, I know, but I have thus far
> > been unable to find a straightforward explanation of viewlets, in
> > terms of how they relate to general site development.
>
> All I can tell you now is : USE VIEWLETS, USE VIEWLETS, USE VIEWLETS,
>
>
> Jürgen
>
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