[Zope] Re: losing random session data

[Tres Seaver]

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Maciej Wisniowski wrote:
>> my data ends up looking like this:
>>
>> order [{}, {}, {'foo': '1', 'bar': 'a'}, {}, {'foo': '2', 'bar': 'b'},
>> {'foo': '6', 'bar': 'z'}, {'foo': '1', 'bar': 'a'}]
> What is wrong here? I mean what output is expected?
> 
>> I've seen  http://mail.zope.org/pipermail/zope-dev/2006-July/027890.html
>> and am aware that related bug existed prior to 2.7.1.
> There is 'faster' that is alternative sessioning machinery but I don't know
> if it works with 2.7

It depends on Five / Zope3:  I haven't used the appropriate versions
(Five 1.0.x, ZopeX3 3.0.x) with it, and don't know whether the faster
product is compatible with them.

>> I've used sessions without problems before, this is the first time I
>> attempt to store variables in containers. What am I doing wrong?
> Maybe it is because of req.form assignment. Try to create copy of
> its values and append this to 'order' list like:
> 
> session = context.REQUEST.SESSION
> order = session.get('order', [])
> order.append({'foo':req.form['foo'],
>               'bar':req.form['bar']})
> session.set('order',order)
> 
> and see what happens now.

Note as well that using "mutable" Python primitives (dicts, lists) is
tricky, as they don't notify *their* container (the persistent
SessionDataObject) when they are mutatated.  If you are using them,
rather than some persistent variant, then you need to rebind them into
the container.  E.g.:

  mapping = SESSION.get('mapping')
  if mapping is None:
      mapping = {}
  mapping['foo'] = REQUEST.form('foo')
  SESSION['mapping'] = mapping  # triggers persistence


Tres.
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Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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