[Zope-CMF] Add attributes to class which already has instances in ZODB

[Raphael Ritz]

Hi Rainer,

Look at the product development chapter in the developers guide
http://www.zope.org/Documentation/Books/ZDG/current/Products.stx
There is a section on "evolving classes". The statements there also
hold for CMF products.

You can even use monkey patching
(http://www.zope.org/Members/Caseman/Dynamic_Hotfix,
there is also a German translation on http://www.dzug.org which
I wrote recently)
to provide the new attribute, its class default and any methods
related to them.

HTH

    Raphael

Rainer Thaden wrote:

>Hi,
>
>let's say you've written a type-class for CMF with some attributes,
>but you are not sure, if there are attributes missing. When you notice
>that there are missing attributes it will be too late to change the
>class, because there are already some instances in the ZODB, which you
>can't assign the new attributes.
>What would you do to prevent this situation when developing the class?
>Is it possible to add some dummy attributes and assign them the
>appropriate name afterwards like
>
>Attribute list:
>  name=''  #'normal' attributes
>  birth=''
>  ext1=''  #dummy attributes
>  ext2=''
>
>  and then you notice that you need an attribute for an email and
>  write 
>
>  email=ext1
>
>  inside the class.
>  
>Will a call to email on the objects which are already in the ZODB
>resolve the right name?
>  
>  
>