Text File
validation.txt

Schema Valiation

There are two helper methods to verify schemas and interfaces:

getValidationErrors
first validates via the zope.schema field validators. If that succeeds the invariants are checked.
getSchemaValidationErrors
only validateds via the zope.schema field validators. The invariants are not checked.

Create an interface to validate against:

>>> import zope.interface
>>> import zope.schema
>>> class ITwoInts(zope.interface.Interface):
...     a = zope.schema.Int(max=10)
...     b = zope.schema.Int(min=5)
...
...     @zope.interface.invariant
...     def a_greater_b(obj):
...         print "Checking if a > b"
...         if obj.a <= obj.b:
...             raise zope.interface.Invalid("%s<=%s" % (obj.a, obj.b))
...

Create a silly model:

>>> class TwoInts(object):
...     pass

Create an instance of TwoInts but do not set attributes. We get two errors:

>>> ti = TwoInts()
>>> zope.schema.getValidationErrors(ITwoInts, ti)
[('a', 'TwoInts' object has no attribute 'a'),
 ('b', 'TwoInts' object has no attribute 'b')]

The getSchemaValidationErrors function returns the same result:

>>> zope.schema.getSchemaValidationErrors(ITwoInts, ti)
[('a', 'TwoInts' object has no attribute 'a'),
 ('b', 'TwoInts' object has no attribute 'b')]

Note that see no error from the invariant because the invariants are not vaildated if there are other schema errors.

When we set an invalid value for a we still get the same error for b:

>>> ti.a = 11
>>> errors = zope.schema.getValidationErrors(ITwoInts, ti)
>>> errors
[('a', 11 10),
 ('b', 'TwoInts' object has no attribute 'b')]
>>> errors[0][1].doc()
u'Value is too big'

After setting a valid value for a there is only the error for the missing b left:

>>> ti.a = 8
>>> zope.schema.getValidationErrors(ITwoInts, ti)
[('b', 'TwoInts' object has no attribute 'b')]

After setting valid value for b the schema is valid so the invariants are checked. As b>a the invariant fails:

>>> ti.b = 10
>>> errors = zope.schema.getValidationErrors(ITwoInts, ti)
Checking if a > b
>>> errors
[(None, <zope.interface.exceptions.Invalid instance at 0x...>)]

When using getSchemaValidationErrors we do not get an error any more:

>>> zope.schema.getSchemaValidationErrors(ITwoInts, ti)
[]

Set b=5 so everything is fine:

>>> ti.b = 5
>>> zope.schema.getValidationErrors(ITwoInts, ti)
Checking if a > b
[]