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pypm install products.references

How to install Products.References

  1. Download and install ActivePython
  2. Open Command Prompt
  3. Type pypm install products.references
 Python 2.7Python 3.2Python 3.3
Windows (32-bit)
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Windows (64-bit)
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Mac OS X (10.5+)
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Linux (32-bit)
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Linux (64-bit)
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Lastest release
version 1.0 on Jan 5th, 2011

A Reference is a Zope object refering to another Zope object, called its Target. The target it identified by a path relative to the parent of the Reference. It is resolved into the target through restrictedTraverse.

The attribute Target as well as the method getTarget give the target object.

A Reference behaves almost like its target. It appears to have (most of) its attributes and methods. In this sense, it is very similar to Shane's Symlink product. Unlike a Symlink, however, a Reference has its own id, title and management facilities and therefore can be distinguished from the refered to object. This is very difficult for a SymLink; therefore, I consider Reference safer.

On lookup, a Reference prefers its own attributes over those of the target. This means that it behaves as a reference and partially as its target.


There are security weaknesses: the setDefaultAccess('allow') and the declareObjectProtected('Access contents information') of Reference spill over to the target when accessed through the reference. This is a side effect of Zope's (strange) security policy.

In order to ensure manageability of the Reference, __before_publishing_traverse__ and __bobo_traverse__ are not relayed to the target.

It is very difficult (I think impossible) to emulate the special treatment of Python Methods by acquisition. The current implementation tries hard to emulate enough that Python Scripts (and similar objects) get correct bindings. However, the acquisition context is otherwise different from how it were when directly called.

Zope toolkit (aka Zope3) adapters (this includes views) may not work on references as you expect because the adapters see the interfaces implemented by the reference itself, not those of the refered to object.

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Last updated Jan 5th, 2011

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