[Grok-dev] How are viewlets better than macros?

Wichert Akkerman wichert at wiggy.net
Mon May 5 12:01:41 EDT 2008

Previously Sebastian Ware wrote:
> On the Grok site viewlets are explained to have "...basically the same  
> purpose as a macro, but is more clean, powerful and flexible." Only  
> the text fails to explain how. The example shown doesn't show much of  
> this power or flexibility as far as I can tell. Where is the real  
> benefit? What am I missing?

They are not 'basically the same'. The concepts are different:

- using viewlet managers you can define 'slots' in a page where things
  can be inserted. 

- a viewlet something that produce a bit of html (the 'thing' from the
  previous point) which can be shown in a viewlet manager. A viewlet
  itself does not know where its output will be included.

- you can register a viewlet for a viewlet manager. That will make its
  output appear in the viewlet manager's slot. A single viewlet manager
  can show many different viewlets, or none at all.

- by tweaking the registrations you can move viewlets from one viewlet manager
  to another, change the ordering, hide them, add new viewlets, all
  without having to touch a single line of code.

The last two are not possible with macros.

Standard viewlet managers do not support ordering. Plone has an
orderable viewletmanager in plone.app.viewletmanager. I don't know if
grok has something similar.


Wichert Akkerman <wichert at wiggy.net>    It is simple to make things.
http://www.wiggy.net/                   It is hard to make things simple.

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