Am 28.05.2008 um 15:44 schrieb Philipp von Weitershausen:

Thanks, that's the explanation I was missing - I hope I'm not the only one who doesn't quite understand what is adapting what when a view is called. 8-)

Um, this is explained in detail in my book. Views are always looked up like this:

 getMultiAdapter( (context, request), name="foo.html" )

(whitespace added for clarification.)

So by applying marker interfaces to the request, we can change the output of that adaption. See pages 168-169 in my book.

I understand the theory. I know that views are adapters but as this is still something I'm not that familiar with and particularly as I don't write a lot of code using them, it's easy to forget what's exactly happening.

class IMySkin(ICustom, ISomethingElse, ICMFDefaultSkin):

<interface interface="...IMyDefaultSkin"

<browser:defaultSkin name="MySkin" />
Okay, this is starting to make sense. Layers and skins are confusing especially as they are all just interfaces!

That's what's so easy about them!

Agreed but it does make the naming interface/layer/skin entirely a matter of convention. Great once you're used to it.

:-O When does the skin name get used apart from in ++skin++ urls?

Wherever you'd like to use it. Perhaps you'd like to show a list of available skins to the user so that s/he can choose one.

Okay - otherwise little relevance for programming?

Views are still registered to layers, ie. interfaces, aren't they?


What I had been expecting to work, but which I think I now understand why it wouldn't, was the ability to add a layer for something like an "administration" layer which would call a version of standard_macros specific to that layer. I was hoping to be able to change this simply in ZCML rather than in the templates, ie. configure the views I want to use a different "skin". Instead, it seems, I need to write and register my own macros and change those templates that need to use them. Not sure whether this is entirely the right way to go about this, as opposed to using a viewlet to do it but as least I've got it to work.

I'm not quite sure I'm following you here. Often skins mostly contain custom macros, meaning all views are registered for some default layer (e.g. IDefaultBrowserLayer) and they look up macros using context/@@standard_macros. Then it's up to the specific skin to provide a standard_macros view. This is the one that defines the look and feel of the site and therefore changes from skin to skin.

I understand this now. My current use case is

This is exactly what my book explains and does (see Exapmles 10.3.2 and 30.3.3)! Forgive my bluntness, but it's hard to believe at this point you've read it...

Reading is not necessarily understanding! This is no criticism of the book which, by the way, I think is exceptionally well written. But as with so many things, some things only click into place when you actually work with them and some things only make sense when you've mastered others.

You're welcome. For the fourth edition, and I hope there will be one, it might be an idea to add a couple of paragraphs from above to clarify customisation by adding a layer, ie. where world_cookery inherits from Rotterdam and where it differs.

The IWorldcookerySkin interface doesn't inherit from Rotterdam. And to be honest, I wouldn't know what else to write. I even have a "Flashback" box that compares Zope 3 style layers to CMF layers and skins on page 173. And what I've written in the two previous emails were mostly rephrased passages from my book anyway.

Well, maybe it's an opportunity for me! ;-)

Thank you very much for taking the time to explain this in greater detail.

Charlie Clark
Helmholtzstr. 20
D- 40215
Tel: +49-211-938-5360
GSM: +49-178-782-6226

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