[Grok-dev] distinguish between a create or an edit situation in a formlib constraint

[Dr. Volker Jaenisch]

Hi Grok-People!

Maybe this should go better to the formlib people
but Grok wrapps formlib in a special way ..

I have property "name" that should be unique

class IKvmInstance(interface.Interface):
    """Defines a KVM instance."""
    name = schema.TextLine(
        title = u'KVM Name',
        default = u'VM1',
        required = True,
        constraint = validateVMName,
    )

In validateVMName I check for the existance of a VM with the same name 
and reject
the request if a VM with the given name already exists.

from zope.schema import ValidationError

class VMNameAlreadyInUse(ValidationError):
        "VM Name already in use"

def validateVMName( name ):
    # Why the heck this is called at grok boot-time??
    if grok.getSite() == None : return True

    if grok.getSite().kvmManager.kvmContainer.has_key( name ):
        raise VMNameAlreadyInUse

    return True

This work fine for the creation but fails on editing a KVMInstance. Is 
there a generically way to do it?
Or will I have to impose a flag on the instance that I check to see that 
the instance is already created?

How can I seperate the creating and the edition use-case programmatically.

Any Hints appreciated

Best Reagards

Volker


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