[Zope3-dev] calling objects when evaluating path expressions

[Marius Gedminas]

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On Fri, Jun 20, 2003 at 06:29:19PM +0300, Steve Alexander wrote:
> >Here's another approach that doesn't add any syntax.  Recently, we added=
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> >the ability to use prefixes in the middle of path expressions, so=20
> >perhaps we could define the "call:" prefix to mean "call the method=20
> >named X, passing no arguments".
> >
> ><span tal:replace=3D"foo/call:bar/baz" />
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> That's very similar to the syntax I jokingly suggested when talking=20
> about this with Jim on irc earlier today:
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>   <span tal:replace=3D"foo/bar/zope:call/baz" />
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> I like your version better though. So, 'call' would essentially be a=20
> proxy that makes no-args methods into gettable properties.
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> >On a related note, a few other prefixes could disambiguate traversal.=20
> >Consider the problem of fetching an item called "keys" from a dictionary=
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> >using a path expression.  Unless Zope 3 has changed the policy, basic=20
> >traversal tries attributes first and items second, so path expressions=
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> >can't easily access items with certain names.
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> Actually, Zope 3 has changed the policy. For speed, and because we use a=
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> lot of dicts, dicts are always traversed using __getitem__.
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> >An "item:" prefix could solve this.
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> It would. This would be useful for containers.

I believe there are already namespaces that accomplish this:

  foo/bar/++attr++xxx/      does getattr(bar, 'xxx')
  foo/bar/++item++yyy/      does bar[yyy]

Adding a ++call++ ought to be trivial (4 lines in namespaces.py + some
zcml).

OTOH foo/call:something/ looks better than foo/++call++something/.

Marius Gedminas
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Codeworks is available for Zope consulting -- http://www.codeworks.lt/

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