LAZR Fields

CollectionField

CollectionField is a field representing an iterable collection. The field provides ICollectionField which is an extension of ISequence.

>>> from zope.schema import Int
>>> from zope.schema.interfaces import ISequence
>>> from lazr.restful.interfaces import ICollectionField
>>> from lazr.restful.fields import CollectionField

>>> int_collection = CollectionField(
...     title='A collection', value_type=Int())

>>> from zope.interface.verify import verifyObject
>>> verifyObject(ICollectionField, int_collection)
True

>>> ICollectionField.extends(ISequence)
True

By default, such fields are readonly.

>>> int_collection.readonly
True

But it can be made read-write.

>>> rw_collection = CollectionField(
...     title='A writable collection.', readonly=False)
>>> rw_collection.readonly
False

The validate method accepts any iterable that satisfy the contained elements.

>>> int_collection.validate(range(10))

But if the object isn’t iterable, NotAContainer is raised.

>>> int_collection.validate(object())
Traceback (most recent call last):
  ...
zope.schema._bootstrapinterfaces.NotAContainer: <object...>

If the iterable contains an invalid item, WrongContainedType is raised.

>>> int_collection.validate(['a', 1, 2, 'b'])
Traceback (most recent call last):
  ...
zope.schema._bootstrapinterfaces.WrongContainedType: ...

Reference

A Reference field is just like an Object except that it doesn’t validate by value, but only check that the value provides the proper schema.

>>> from zope.interface import Interface, directlyProvides
>>> from zope.schema import Text
>>> class MySchema(Interface):
...     a_value = Text()

>>> from lazr.restful.fields import Reference
>>> from lazr.restful.interfaces import IReference

>>> reference = Reference(schema=MySchema)
>>> verifyObject(IReference, reference)
True

>>> class Fake:
...     pass
>>> fake = Fake()
>>> reference.validate(fake)
Traceback (most recent call last):
  ...
zope.schema._bootstrapinterfaces.SchemaNotProvided: ...

>>> directlyProvides(fake, MySchema)
>>> reference.validate(fake)

The Reference field supports the standard IField constraint.

>>> reference = Reference(
...     schema=MySchema,
...     constraint=lambda value: 'good' in value.a_value)

>>> fake.a_value = 'bad'
>>> reference.validate(fake)
Traceback (most recent call last):
  ...
zope.schema._bootstrapinterfaces.ConstraintNotSatisfied: ...

>>> fake.a_value = 'good'
>>> reference.validate(fake)