plone.registry 1.0b3

============
Introduction
============

This package provides debconf-like (or about:config-like) settings registries
for Zope applications. A `registry`, with a dict-like API, is used to get and
set values stored in `records`. Each record contains the actual value, as
well as a `field` that describes the record in more detail. At a minimum, the
field contains information about the type of value allowed, as well as a short
title describing the record's purpose.

See the following doctests for more details:

* `registry.txt`, which demonstrates how registries and records work
* `events.txt`, which shows the events that are fired from the registry
* `field.txt`, which describes the behaviour of persistent fields


Changelog
=========

1.0b3 - 2011-01-03
------------------

* added prefix option to forInterface (as it was added to registerInterface)
[garbas]

1.0b2 - 2010-04-21
------------------

* Added support for Decimal fields
[optilude]

* Add a prefix option to registerInterface to allow an interface to be used as
a template for a series of values, rather than single use.
[MatthewWilkes]

1.0b1 - 2009-08-02
------------------

* Fix a bug in bind() for Choice fields.
[optilude]

1.0a2 - 2009-07-12
------------------

* Changed API methods and arguments to mixedCase to be more consistent with
the rest of Zope. This is a non-backwards-compatible change. Our profuse
apologies, but it's now or never. :-/

If you find that you get import errors or unknown keyword arguments in your
code, please change names from foo_bar too fooBar, e.g. for_interface()
becomes forInterface().
[optilude]

1.0a1 - 2009-04-17
------------------

* Initial release

================
Using registries
================

You can create a new registry simply by instantiating the Registry class. The
class and its data structures are persistent, so you can store them in the
ZODB. You may want to provide the registry object as local utility for easy
access as well, though we won't do that here.

>>> from plone.registry import Registry
>>> registry = Registry()

The registry starts out empty. To access the registry's records, you can use
the `records` property. This exposes a dict API where keys are strings and
values are objects providing `IRecords`.

>>> len(registry.records)
0

Simple records
==============

Let's now create a record. A record must have a name. This should be a dotted
name, and contain ASCII characters only. By convention, it should be all
lowercase and start with the name of the package that defines the record.

It is also possible to create a number of records based on a single schema
interface - see below - but for now, we will focus on simple records.

Before we can create the record, we must create the field that describes it.
Fields are based on the venerable zope.schema package, but plone.registry
only supports certain fields, and disallows use of a few properties even
of those. As a rule of thumb, so long as a field stores a Python primitive,
it is supported; the same goes for attributes of fields.

Thus:

* Fields like `Object`, `InterfaceField` and so on are not supported
* A custom `constraint` method is not supported.
* The `order` attribute will always be set to -1
* For Choice fields, only named vocabularies are supported: you cannot
reference a particular source or source binder
* The key_type and value_type properties of Dict, List, Tuple, Set and
Frozenset may only contain persistent fields.

See field.text for more details.

Creating a record
-----------------

The supported field types are found in the module plone.registry.field. These
are named the same as the equivalent field in zope.schema, and have the same
constructors. You must use one of these fields when creating records directly.

>>> from plone.registry import field
>>> age_field = field.Int(title=u"Age", min=0, default=18)

>>> from plone.registry import Record
>>> age_record = Record(age_field)

Note that in this case, we did not supply a value. The value will therefore
be the field default.

>>> age_record.value
18

We can set a different value, either in the `Record` constructor or via the
`value` attribute:

>>> age_record.value = 2
>>> age_record.value
2

Note that the value is validated against the field:

>>> age_record.value = -1
Traceback (most recent call last):
...
TooSmall: (-1, 0)

>>> age_record.value
2

We can now add the field to the registry. This is done via the `record`
dictionary.

>>> 'plone.records.tests.age' in registry
False
>>> registry.records['plone.records.tests.age'] = age_record

At this point, the record will gain __name__ and __parent__ attributes.

>>> age_record.__name__
'plone.records.tests.age'

>>> age_record.__parent__ is registry
True

Creating a record with an initial value
---------------------------------------

We can create records more succinctly by creating the field, setting the value
and assigning it to the registry in one go, like this:

>>> registry.records['plone.records.tests.cms'] = \
... Record(field.TextLine(title=u"CMS of choice"), u"Plone")

The record can now be obtained. Note that it has a nice __repr__ to help
debugging.

>>> registry.records['plone.records.tests.cms']
<Record plone.records.tests.cms>

Accessing and manipulating record values
----------------------------------------

Once a record has been created and added to the registry, you can access
its value through dict-like operations on the registry itself.

>>> 'plone.records.tests.cms' in registry
True

>>> registry['plone.records.tests.cms']
u'Plone'

>>> registry['plone.records.tests.cms'] = u"Plone 3.x"

Again, values are validated:

>>> registry['plone.records.tests.cms'] = 'Joomla'
Traceback (most recent call last):
...
WrongType: ('Joomla', <type 'unicode'>...)

There is also a get() method:

>>> registry.get('plone.records.tests.cms')
u'Plone 3.x'
>>> registry.get('non-existent-key') is None
True

Deleting records
----------------

Records may be deleted from the `records` property:

>>> del registry.records['plone.records.tests.cms']
>>> 'plone.records.tests.cms' in registry.records
False
>>> 'plone.records.tests.cms' in registry
False

Creating records from interfaces
================================

As an application developer, it is often desirable to define settings as
traditional interfaces with zope.schema fields. plone.registry includes
support for creating a set of records from a single interface.

To test this, we have created an interface, `IMailSettings`, with two fields,
`sender` and `smtp_host`.

>>> from plone.registry.tests import IMailSettings

Note that this contains standard fields.

>>> IMailSettings['sender']
<zope.schema._bootstrapfields.TextLine object at ...>

>>> IMailSettings['smtp_host']
<zope.schema._field.URI object at ...>

We can create records from this interface like this:

>>> registry.registerInterface(IMailSettings)

One record for each field in the interface has now been created. Their names
are the full dotted names to those fields:

>>> sender_record = registry.records['plone.registry.tests.IMailSettings.sender']
>>> smtp_host_record = registry.records['plone.registry.tests.IMailSettings.smtp_host']

The fields used in the records will be the equivalent persistent versions of
the fields from the original interface.

>>> sender_record.field
<plone.registry.field.TextLine object at ...>

>>> smtp_host_record.field
<plone.registry.field.URI object at ...>

This feat is accomplished internally by adapting the field to the
IPersistentField interface. There is a default adapter factory that works for
all fields defined in plone.registry.field. You can of course define your own
adapter if you have a custom field type, but bear in mind the golden rules of
any persistent field:

* The field must store only primitives or other persistent fields
* It must not reference a function, class, interface or other method that
could break if a package is uninstalled.

If we have a field for which there is no IPersistentField adapter, we will
get an error:

>>> from plone.registry.tests import IMailPreferences
>>> IMailPreferences['settings']
<zope.schema._field.Object object at ...>

>>> registry.registerInterface(IMailPreferences)
Traceback (most recent call last):
...
TypeError: There is no persistent field equivalent for the field `settings` of type `Object`.

Whoops! We can, however, tell registerInterface() to ignore one or more
fields.

>>> registry.registerInterface(IMailPreferences, omit=('settings',))

Once an interface's records have been registered, we can get and set their
values as normal:

>>> registry['plone.registry.tests.IMailSettings.sender']
u'root@localhost'

>>> registry['plone.registry.tests.IMailSettings.sender'] = u"webmaster@localhost"
>>> registry['plone.registry.tests.IMailSettings.sender']
u'webmaster@localhost'

If we sub-sequently re-register the same interface, the value will be retained
if possible:

>>> registry.registerInterface(IMailSettings)
>>> registry['plone.registry.tests.IMailSettings.sender']
u'webmaster@localhost'

However, if the value is no longer valid, we will revert to the default. To
test that, let's sneakily modify the field for a while.

>>> old_field = IMailSettings['sender']
>>> IMailSettings._InterfaceClass__attrs['sender'] = field.Int(title=u"Definitely not a string", default=2)
>>> if hasattr(IMailSettings, '_v_attrs'):
... del IMailSettings._v_attrs['sender']
>>> registry.registerInterface(IMailSettings)
>>> registry['plone.registry.tests.IMailSettings.sender']
2

But let's put it back the way it was.

>>> IMailSettings._InterfaceClass__attrs['sender'] = old_field
>>> if hasattr(IMailSettings, '_v_attrs'):
... del IMailSettings._v_attrs['sender']
>>> registry.registerInterface(IMailSettings)
>>> registry['plone.registry.tests.IMailSettings.sender']
u'root@localhost'

Sometimes, you may want to use an interface as a template for multiple
instances of a set of fields, rather than defining them all by hand. This is
especially useful when you want to allow third-party packages to provide
information. To accomplish this, we can provide a prefix with the
`registerInterface' call. This will take precedence over the __identifier__
that is usually used.

>>> registry.registerInterface(IMailSettings, prefix="plone.registry.tests.alternativesettings")

These values are now available in the same way as the original settings:

>>> sender_record = registry.records['plone.registry.tests.alternativesettings.sender']
>>> smtp_host_record = registry.records['plone.registry.tests.alternativesettings.smtp_host']


Accessing the original interface
--------------------------------

Now that we have these records, we can look up the original interface. This
does not break the golden rules: internally, we only store the name of the
interface, and resolve it at runtime.

Records that know about interfaces are marked with `IInterfaceAwareRecord` and
have two additional properties: `interface` and `fieldName`.

>>> from plone.registry.interfaces import IInterfaceAwareRecord
>>> IInterfaceAwareRecord.providedBy(age_record)
False
>>> IInterfaceAwareRecord.providedBy(sender_record)
True

>>> sender_record.interfaceName
'plone.registry.tests.IMailSettings'

>>> sender_record.interface is IMailSettings
True

Using the records proxy
-----------------------

Once the records for an interface has been created, it is possible to obtain
a proxy object that provides the given interface, but reads and writes its
values to the registry. This is useful, for example, to create a form using
`zope.formlib` or `z3c.form` that is configured with widgets based on the
interface, or simply as a more convenient API when working with multiple,
related settings.

>>> proxy = registry.forInterface(IMailSettings)
>>> proxy
<RecordsProxy for plone.registry.tests.IMailSettings>

If you use your registry values in code
which might be encountered on normal HTML rendering
paths (e.g. in a viewlet) you need to be aware that records
might not exist or they are invalid. `forInterface()`
will raise KeyError on this kind of situations::

try:
proxy = registry.forInterface(IMailSettings)
except KeyError:
# Gracefully handled cases
# when GenericSetup installer has not been run or rerun
# e.g. by returning or using some default values
pass

The proxy is not a persistent object on its own.

>>> from persistent.interfaces import IPersistent
>>> IPersistent.providedBy(proxy)
False

It does, however, provide the requisite interface.

>>> IMailSettings.providedBy(proxy)
True

You can distinguish between the proxy and a 'norma' object by checking for the
IRecordsProxy marker interface:

>>> from plone.registry.interfaces import IRecordsProxy
>>> IRecordsProxy.providedBy(proxy)
True

When we set a value, it is stored in the registry:

>>> proxy.smtp_host = 'http://mail.server.com'
>>> registry['plone.registry.tests.IMailSettings.smtp_host']
'http://mail.server.com'

>>> registry['plone.registry.tests.IMailSettings.smtp_host'] = 'smtp://mail.server.com'
>>> proxy.smtp_host
'smtp://mail.server.com'

Values not in the interface will raise an AttributeError:

>>> proxy.age
Traceback (most recent call last):
...
AttributeError: age

Note that by default, the forInterface() method will check that the necessary
records have been registered. For example, we cannot use any old interface:

>>> registry.forInterface(IInterfaceAwareRecord)
Traceback (most recent call last):
...
KeyError: 'Interface `plone.registry.interfaces.IInterfaceAwareRecord` defines a field `interface`, for which there is no record.'

By default, we also cannot use an interface for which only some records exist:

>>> registry.forInterface(IMailPreferences)
Traceback (most recent call last):
...
KeyError: 'Interface `plone.registry.tests.IMailPreferences` defines a field `settings`, for which there is no record.'

It is possible to disable this check, however. This will be a bit more
efficient:

>>> registry.forInterface(IMailPreferences, check=False)
<RecordsProxy for plone.registry.tests.IMailPreferences>

A better way, however, is to explicitly declare that some fields are omitted:

>>> pref_proxy = registry.forInterface(IMailPreferences, omit=('settings',))

In this case, the omitted fields will default to their 'missing' value:

>>> pref_proxy.settings == IMailPreferences['settings'].missing_value
True

However, trying to set the value will result in a AttributeError:

>>> pref_proxy.settings = None
Traceback (most recent call last):
...
AttributeError: settings

===============
Registry events
===============

The registry fires certain events. These are:

* `plone.registry.interfaces.IRecordAddedEvent`, when a record has been
added to the registry.

* `plone.registry.interfaces.IRecordRemovedEvent`, when a record has been
removed from the registry.

* `plone.registry.interfaces.IRecordModifiedEvent`, when a record's value is
modified.

To test these events, we will create, modify and remove a few records:

>>> from plone.registry import Registry, Record, field
>>> registry = Registry()

Adding a new record to the registry should fire IRecordAddedEvents:

>>> registry.records['plone.registry.tests.age'] = \
... Record(field.Int(title=u"Age", min=0, default=18))

>>> registry.records['plone.registry.tests.cms'] = \
... Record(field.TextLine(title=u"Preferred CMS"), value=u"Plone")

When creating records from an interface, one event is fired for each field
in the interface.

>>> from plone.registry.tests import IMailSettings
>>> registry.registerInterface(IMailSettings)

Deleting a record should fire an IRecordRemovedEvent:

>>> del registry.records['plone.registry.tests.cms']

Changing a record should fire an IRecordModifiedEvent:

>>> registry['plone.registry.tests.age'] = 25
>>> registry.records['plone.registry.tests.age'].value = 24

Let's take a look at the events that were just fired:

>>> from plone.registry.interfaces import IRecordEvent
>>> from zope.component.eventtesting import getEvents
>>> getEvents(IRecordEvent)
[<RecordAddedEvent for plone.registry.tests.age>,
<RecordAddedEvent for plone.registry.tests.cms>,
<RecordAddedEvent for plone.registry.tests.IMailSettings.sender>,
<RecordAddedEvent for plone.registry.tests.IMailSettings.smtp_host>,
<RecordRemovedEvent for plone.registry.tests.cms>,
<RecordModifiedEvent for plone.registry.tests.age>,
<RecordModifiedEvent for plone.registry.tests.age>]

For the modified events, we can also check the value before and after the
change.

>>> from plone.registry.interfaces import IRecordModifiedEvent
>>> [(repr(e), e.oldValue, e.newValue,) for e in getEvents(IRecordModifiedEvent)]
[('<RecordModifiedEvent for plone.registry.tests.age>', 18, 25),
('<RecordModifiedEvent for plone.registry.tests.age>', 25, 24)]

IObjectEvent-style redispatchers
================================

There is a special event handler which takes care of re-dispatching registry
events based on the schema interface prescribed by the record.

Let's re-set the event testing framework and register the re-dispatching event
subscriber. Normally, this would happen automatically by including this
package's ZCML.

>>> from zope.component.eventtesting import clearEvents
>>> from zope.component import provideHandler
>>> from plone.registry.events import redispatchInterfaceAwareRecordEvents
>>> clearEvents()
>>> provideHandler(redispatchInterfaceAwareRecordEvents)

We'll then register a schema interface.

>>> from plone.registry.tests import IMailSettings
>>> registry.registerInterface(IMailSettings)

We could now register an event handler to print any record event occurring on
an IMailSettings record. More specialised event handlers for e.g.
IRecordModifiedEvent or IRecordRemovedEvent are of course also possible.
Note that it is not possible to re-dispatch IRecordAddedEvents, so these are
never caught.

>>> from zope.component import adapter
>>> @adapter(IMailSettings, IRecordEvent)
... def print_mail_settings_events(proxy, event):
... print "Got", event, "for", proxy
>>> provideHandler(print_mail_settings_events)

Let's now modify one of the records for this interface. The event handler
should react immediately.

>>> registry['plone.registry.tests.IMailSettings.sender'] = u"Some sender"
Got <RecordModifiedEvent for plone.registry.tests.IMailSettings.sender> for <RecordsProxy for plone.registry.tests.IMailSettings>

Let's also modify a non-interface-aware record, for comparison's sake. Here,
there is nothing printed.

>>> registry['plone.registry.tests.age'] = 3

We can try a record-removed event as well:

>>> del registry.records['plone.registry.tests.IMailSettings.sender']
Got <RecordRemovedEvent for plone.registry.tests.IMailSettings.sender> for <RecordsProxy for plone.registry.tests.IMailSettings>

The basic events that have been dispatched are:

>>> getEvents(IRecordEvent)
[<RecordAddedEvent for plone.registry.tests.IMailSettings.sender>,
<RecordAddedEvent for plone.registry.tests.IMailSettings.smtp_host>,
<RecordModifiedEvent for plone.registry.tests.IMailSettings.sender>,
<RecordModifiedEvent for plone.registry.tests.age>,
<RecordRemovedEvent for plone.registry.tests.IMailSettings.sender>]

=================
Persistent fields
=================

The persistent fields that are found in plone.registry.field are siblings of
the ones found in zope.schema, with persistence mixed in. To avoid potentially
breaking the registry with persistent references to symbols that may go away,
we purposefully limit the number of fields supported. We also disallow some
properties, and add some additional checks on others.

The standard fields
====================

We will show each supported field in turn. For all fields, note that:

* the `order` property will return -1 no matter what
* setting the `constraint` property is diallowed
* the `key_type` and `value_type` properties, where applicable, must be set
to a persistent field.
* for `Choice` fields, only named vocabularies and vocabularies based on
simple values are supported: sources and IVocabulary objects are not.

>>> from plone.registry import field
>>> from zope import schema
>>> from persistent import Persistent

Bytes
-----

The bytes field describes a string of bytes.

>>> f = field.Bytes(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.Bytes)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Bytes(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint('ABC')
True

BytesLine
---------

The bytes field describes a string of bytes, disallowing newlines.

>>> f = field.BytesLine(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.BytesLine)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.BytesLine(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint('AB\nC')
False

ASCII
-----

The ASCII field describes a string containing only ASCII characters.

>>> f = field.ASCII(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.ASCII)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.ASCII(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint('ab\nc')
True

ASCIILine
---------

The ASCII line field describes a string containing only ASCII characters and
disallowing newlines.

>>> f = field.ASCIILine(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.ASCIILine)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.ASCIILine(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint('ab\nc')
False

Text
----

The text field describes a unicode string.

>>> f = field.Text(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.Text)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Text(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(u'ab\nc')
True

TextLine
--------

The text line field describes a unicode string, disallowing newlines

>>> f = field.TextLine(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.TextLine)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.TextLine(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(u'ab\nc')
False

Bool
----

The bool field describes a boolean.

>>> f = field.Bool(title=u"Test")
>>> isinstance(f, schema.Bool)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Bool(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(False)
True

Int
---

The int field describes an integer or long.

>>> f = field.Int(title=u"Test", min=-123, max=1234)
>>> isinstance(f, schema.Int)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Int(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(123)
True

Float
-----

The float field describes a float.

>>> f = field.Float(title=u"Test", min=-123.0, max=1234.0)
>>> isinstance(f, schema.Float)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Float(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(123)
True

Decimal
-------

The decimal field describes a decimal.

>>> import decimal
>>> f = field.Decimal(title=u"Test", min=decimal.Decimal('-123.0'), max=decimal.Decimal('1234.0'))
>>> isinstance(f, schema.Decimal)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Decimal(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(123)
True

Password
--------

The password field describes a unicode string used for a password.

>>> f = field.Password(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.Password)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Password(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(u'ab\nc')
False

SourceText
----------

The source text field describes a unicode string with source code.

>>> f = field.SourceText(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.SourceText)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.SourceText(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(u'ab\nc')
True

URI
---

The URI field describes a URI string.

>>> f = field.URI(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.URI)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.URI(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(u'abc')
True

Id
--

The id field describes a URI string or a dotted name.

>>> f = field.Id(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.Id)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Id(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(u'abc')
True

DottedName
----------

The dotted name field describes a dotted name.

>>> f = field.DottedName(title=u"Test", min_length=0, max_length=10)
>>> isinstance(f, schema.DottedName)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.DottedName(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(u'abc')
True

Datetime
--------

The date/time field describes a Python datetime object.

>>> f = field.Datetime(title=u"Test")
>>> isinstance(f, schema.Datetime)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Datetime(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> import datetime
>>> f.constraint(datetime.datetime.now())
True

Date
----

The date field describes a Python date object.

>>> f = field.Date(title=u"Test")
>>> isinstance(f, schema.Date)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Date(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> import datetime
>>> f.constraint(datetime.date.today())
True

Timedelta
---------

The time-delta field describes a Python timedelta object.

>>> f = field.Timedelta(title=u"Test")
>>> isinstance(f, schema.Timedelta)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Timedelta(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> import datetime
>>> f.constraint(datetime.timedelta(1))
True

Tuple
-----

The tuple field describes a tuple.

>>> f = field.Tuple(title=u"Test", min_length=0, max_length=10,
... value_type=field.TextLine(title=u"Value"))
>>> isinstance(f, schema.Tuple)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Tuple(title=u"Test", min_length=0, max_length=10,
... value_type=schema.TextLine(title=u"Value"))
Traceback (most recent call last):
...
ValueError: The property `value_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> f.value_type = schema.TextLine(title=u"Value")
Traceback (most recent call last):
...
ValueError: The property `value_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> field.Tuple(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint((1,2))
True

List
----

The list field describes a tuple.

>>> f = field.List(title=u"Test", min_length=0, max_length=10,
... value_type=field.TextLine(title=u"Value"))
>>> isinstance(f, schema.List)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.List(title=u"Test", min_length=0, max_length=10,
... value_type=schema.TextLine(title=u"Value"))
Traceback (most recent call last):
...
ValueError: The property `value_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> f.value_type = schema.TextLine(title=u"Value")
Traceback (most recent call last):
...
ValueError: The property `value_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> field.List(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint([1,2])
True

Set
---

The set field describes a set.

>>> f = field.Set(title=u"Test", min_length=0, max_length=10,
... value_type=field.TextLine(title=u"Value"))
>>> isinstance(f, schema.Set)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Set(title=u"Test", min_length=0, max_length=10,
... value_type=schema.TextLine(title=u"Value"))
Traceback (most recent call last):
...
ValueError: The property `value_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> f.value_type = schema.TextLine(title=u"Value")
Traceback (most recent call last):
...
ValueError: The property `value_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> field.Set(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(set([1,2]))
True

Frozenset
---------

The set field describes a frozenset.

>>> f = field.FrozenSet(title=u"Test", min_length=0, max_length=10,
... value_type=field.TextLine(title=u"Value"))
>>> isinstance(f, schema.FrozenSet)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.FrozenSet(title=u"Test", min_length=0, max_length=10,
... value_type=schema.TextLine(title=u"Value"))
Traceback (most recent call last):
...
ValueError: The property `value_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> f.value_type = schema.TextLine(title=u"Value")
Traceback (most recent call last):
...
ValueError: The property `value_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> field.FrozenSet(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(frozenset([1,2]))
True

Dict
----

The set field describes a dict.

>>> f = field.Dict(title=u"Test", min_length=0, max_length=10,
... key_type=field.ASCII(title=u"Key"),
... value_type=field.TextLine(title=u"Value"))
>>> isinstance(f, schema.Dict)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

>>> field.Dict(title=u"Test", min_length=0, max_length=10,
... key_type=schema.ASCII(title=u"Key"),
... value_type=field.TextLine(title=u"Value"))
Traceback (most recent call last):
...
ValueError: The property `key_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> f.key_type = schema.ASCII(title=u"Key")
Traceback (most recent call last):
...
ValueError: The property `key_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> field.Dict(title=u"Test", min_length=0, max_length=10,
... key_type=field.ASCII(title=u"Key"),
... value_type=schema.TextLine(title=u"Value"))
Traceback (most recent call last):
...
ValueError: The property `value_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> f.value_type = schema.TextLine(title=u"Value")
Traceback (most recent call last):
...
ValueError: The property `value_type` may only contain objects providing `plone.registry.interfaces.IPersistentField`.

>>> field.Dict(title=u"Test", constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint(dict())
True

Choice
------

A choice field represents a selection from a vocabulary. For persistent
fields, the vocabulary cannot be a `source` or any kind of object: it must
either be a list of primitives, or a named vocabulary.

>>> f = field.Choice(title=u"Test", values=[1,2,3])
>>> isinstance(f, schema.Choice)
True
>>> isinstance(f, Persistent)
True

>>> f.order
-1

With a list of values given, the `vocabulary` property returns a vocabulary
constructed from the values on the fly, and `vocabularyName` is None.

>>> f.vocabulary
<zope.schema.vocabulary.SimpleVocabulary object at ...>

>>> f.vocabularyName is None
True

We will, however, get an error if we use anything other than primitives:

>>> f = field.Choice(title=u"Test", values=[object(), object()])
Traceback (most recent call last):
...
ValueError: Vocabulary values may only contain primitive values.

If a vocabulary name given, it is stored in `vocabularyName`, and the
`vocabulary` property returns None.

>>> f = field.Choice(title=u"Test", vocabulary='my.vocab')
>>> f.vocabulary is None
True

>>> f.vocabularyName
'my.vocab'

Other combinations are now allowed, such as specifying no vocabulary:

>>> field.Choice(title=u"Test")
Traceback (most recent call last):
...
AssertionError: You must specify either values or vocabulary.

Or specifying both types:

>>> field.Choice(title=u"Test", values=[1,2,3], vocabulary='my.vocab')
Traceback (most recent call last):
...
AssertionError: You cannot specify both values and vocabulary.

Or specifying an object source:

>>> from zope.schema.vocabulary import SimpleVocabulary
>>> dummy_vocabulary = SimpleVocabulary.fromValues([1,2,3])
>>> field.Choice(title=u"Test", source=dummy_vocabulary)
Traceback (most recent call last):
...
ValueError: Persistent fields do not support sources, only named vocabularies or vocabularies based on simple value sets.

Or specifying an object vocabulary:

>>> field.Choice(title=u"Test", vocabulary=dummy_vocabulary)
Traceback (most recent call last):
...
ValueError: Persistent fields only support named vocabularies or vocabularies based on simple value sets.

As with other fields, you also cannot set a constraint:

>>> field.Choice(title=u"Test", values=[1,2,3], constraint=lambda x: True)
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint = lambda x: False
Traceback (most recent call last):
...
ValueError: Persistent fields does not support setting the `constraint` property

>>> f.constraint('ABC')
True

IPersistentField adapters
=========================

It is possible to adapt any non-persistent field to its related
IPersistentField using the adapter factories in plone.registry.fieldfactory.
These are set up in configure.zcml and explicitly registered in the test
setup in tests.py. Custom adapters are of course also possible.

>>> from plone.registry.interfaces import IPersistentField

>>> f = schema.TextLine(title=u"Test")
>>> IPersistentField.providedBy(f)
False

>>> p = IPersistentField(f)
>>> IPersistentField.providedBy(p)
True

>>> isinstance(p, field.TextLine)
True

Unsupported field types will not be adaptable by default.

>>> f = schema.Object(title=u"Object", schema=IPersistentField)
>>> IPersistentField(f, None) is None
True

>>> f = schema.InterfaceField(title=u"Interface")
>>> IPersistentField(f, None) is None
True

After adaptation, the rules of persistent fields apply: The `order` attribute
is perpetually -1, custom constraints are not allowed, and key and value type
will be adapted to persistent fields as well. If any of these constraints
cannot be met, the adaptation will fail.

For constraints, the non-persistent value is simply ignored and the default
method from the class will be used.

>>> f = schema.TextLine(title=u"Test", constraint=lambda x: False)
>>> f.constraint
<function <lambda> at ...>

>>> p = IPersistentField(f)
>>> p.constraint
<bound method TextLine.constraint of <plone.registry.field.TextLine object at ...>>

The order property is similarly ignored:

>>> f.order > 0
True

>>> p.order
-1

Key/value types will be adapted if possible.

>>> f = schema.Dict(title=u"Test",
... key_type=schema.Id(title=u"Id"),
... value_type=schema.TextLine(title=u"Value"))
>>> p = IPersistentField(f)
>>> p.key_type
<plone.registry.field.Id object at ...>

>>> p.value_type
<plone.registry.field.TextLine object at ...>

However, if they cannot be adapted, there will be an error.

>>> f = schema.Dict(title=u"Test",
... key_type=schema.Id(title=u"Id"),
... value_type=schema.Object(title=u"Value", schema=IPersistentField))
>>> p = IPersistentField(f)
Traceback (most recent call last):
...
TypeError: ('Could not adapt', <zope.schema._field.Dict object at ...>, <InterfaceClass plone.registry.interfaces.IPersistentField>)

>>> f = schema.Dict(title=u"Test",
... key_type=schema.InterfaceField(title=u"Id"),
... value_type=schema.TextLine(title=u"Value"))
>>> p = IPersistentField(f)
Traceback (most recent call last):
...
TypeError: ('Could not adapt', <zope.schema._field.Dict object at ...>, <InterfaceClass plone.registry.interfaces.IPersistentField>)

There is additional validation for choice fields that warrant a custom
adapter. These ensure that vocabularies are either stored as a list of
simple values, or as named vocabularies.

>>> f = schema.Choice(title=u"Test", values=[1,2,3])
>>> p = IPersistentField(f)
>>> p.vocabulary
<zope.schema.vocabulary.SimpleVocabulary object at ...>
>>> p._values
[1, 2, 3]
>>> p.vocabularyName is None
True

>>> f = schema.Choice(title=u"Test", vocabulary='my.vocab')
>>> p = IPersistentField(f)
>>> p.vocabulary is None
True
>>> p._values is None
True
>>> p.vocabularyName
'my.vocab'

Complex vocabularies or sources are not allowed:

>>> from zope.schema.vocabulary import SimpleVocabulary
>>> dummy_vocabulary = SimpleVocabulary.fromItems([('a', 1), ('b', 2)])
>>> f = schema.Choice(title=u"Test", source=dummy_vocabulary)
>>> p = IPersistentField(f)
Traceback (most recent call last):
...
TypeError: ('Could not adapt', <zope.schema._field.Choice object at ...>, <InterfaceClass plone.registry.interfaces.IPersistentField>)


>>> f = schema.Choice(title=u"Test", vocabulary=dummy_vocabulary)
>>> p = IPersistentField(f)
Traceback (most recent call last):
...
TypeError: ('Could not adapt', <zope.schema._field.Choice object at ...>, <InterfaceClass plone.registry.interfaces.IPersistentField>)