Fields

by Martin Aspeli — last modified Oct 10, 2009 03:12 PM

The standard schema fields

The following tables shows the most common field types for use in Dexterity schemata. See the documentation on creating schemata for information about how to use these.

Field properties

Fields are initialised with properties passed in their constructors. To avoid having to repeat the available properties for each field, we'll list them once here, grouped into the interfaces that describe them. You'll see those interfaces again in the tables below that describe the various field types. Refer to the table below to see what properties a particular interface implies.

Interface	Property	Type	Description
IField	title	unicode	The title of the field. Used in the widget.
	description	unicode	A description for the field. Used in the widget.
	required	bool	Whether or not the field is required. Used for form validation. The default is True.
	readonly	bool	Whether or not the field is read-only. Default is False.
	default		The default value for the field. Used in forms and sometimes as a fallback value. Must be a valid value for the field if set. The default is None.
	missing_value		A value that represents "this field is not set". Used by form validation. Defaults to None. For lists and tuples, it is sometimes useful to set this to an empty list/tuple.
IMinMaxLen	min_length	int	The minimum required length. Used for string fields. Default is 0.
	max_length	int	The maximum allowed length. Used for string fields. Default is None (no check).
IMinMax	min		The minimum allowed value. Must be a valid value for the field, e.g. for an Int field this should be an integer. Default is None (no check).
	max		The maximum allowed value. Must be a valid value for the field, e.g. for an Int field this should be an integer. Default is None (no check).
ICollection	value_type		Another Field instance that describes the allowable values in a list, tuple or other collection. Must be set for any collection field. One common usage is to set this to a Choice, to model a multi-selection field with a vocabulary.
	unique	bool	Whether or not values in the collection must be unique. Usually not set directly - use a Set or Frozenset to guarantee uniqueness in an efficient way.
IDict	key_type		Another Field instance that describes the allowable keys in a dictionary. Similar to the value_type of a collection. Must be set.
	value_type		Another Field instance that describes the allowable values in a dictionary. Similar to the value_type of a collection. Must be set.
IObject	schema	Interface	An interface that must be provided by any object stored in this field.
IRichText	default_mime_type	str	Default MIME type for the input text of a rich text field. Defaults to text/html.
	output_mime_type	str	Default output MIME type for the transformed value of a rich text field. Defaults to text/x-html-safe. There must be a transformation chain in the portal_transforms tool that can transform from the input value to the output value for the output property of the RichValue object to contain a value.
	allowed_mime_types	tuple	A list of allowed input MIME types. The default is None, in which case the site-wide settings (from the Markup control panel) will be used.

Field types

The following tables describe the most commonly used field types, grouped by the module from which they can be imported.

Fields in zope.schema

Name	Type	Description	Properties
Choice	N/A	Used to model selection from a voacabulary, which must be supplied. Often used as the value_type of a selection field. The value type is the value of the terms in the vocabulary.	See vocabularies.
Bytes	str	Used for binary data.	IField, IMinMaxLen
ASCII	str	ASCII text (multi-line)	IField, IMinMaxLen
BytesLine	str	A single line of binary data, i.e. a Bytes with newlines disallowed	IField, IMinMaxLen
ASCIILine	str	A single line of ASCII text	IField, IMinMaxLen
Text	unicode	Unicode text (multi-line). Often used with a WYSIWYG widget, although the default is a text area.	IField, IMinMaxLen
TextLine	unicode	A single line of Unicode text	IField, IMinMaxLen
Bool	bool	True or False	IField
Int	int, long	An integer number. Both ints and longs are allowed.	IField, IMinMax
Float	float	A floating point number.	IField, IMinMax
Tuple	tuple	A tuple (non-mutable)	IField, ICollection, IMinMaxLen
List	list	A list	IField, ICollection, IMinMaxLen
Set	set	A set	IField, ICollection, IMinMaxLen
Frozenset	frozenset	A frozenset (non-mutable)	IField, ICollection, IMinMaxLen
Password	unicode	Stores a simple string, but implies a password widget.	IField, IMinMaxLen
Dict	dict	Stores a dictionary. Both key_type and value_type must be set to fields.	IField, IMinMaxLen, IDict
Datetime	datetime	Stores a Python datetime (not a Zope 2 DateTime)	IField, IMinMax
Date	date	Stores a python date	IField, IMinMax
Timedelta	timedelta	Stores a python timedelta	IField, IMinMax
SourceText	unicode	A textfield intended to store source text (e.g. HTML or Python code)	IField, IMinMaxLen
Object	N/A	Stores a Python object that conforms to the interface given as the schema. There is no standard widget for this.	IField, IObject
URI	str	A URI (URL) string	IField, MinMaxLen
Id	str	A unique identifier - either a URI or a dotted name.	IField, IMinMaxLen
DottedName	str	A dotted name string.	IField, IMinMaxLen
InterfaceField	Interface	A Zope interface.	IField
Decimal	Decimal	Stores a Python Decimal. Requires version 3.4 or later of zope.schema. Not available by default in Zope 2.10.	IField, IMinMax

Fields in plone.namedfile.field

See plone.namedfile and plone.formwidget.namedfile for more details.

Name	Type	Description	Properties
NamedFile	NamedFile	A binary uploaded file. Normally used with the widget from plone.formwidget.namedfile.	IField
NamedImage	NamedImage	A binary uploaded image. Normally used with the widget from plone.formwidget.namedfile.	IField
NamedBlobFile	NamedBlobFile	A binary uploaded file stored as a ZODB BLOB. Requires the [blobs] extra to plone.namedfile. Otherwise identical to NamedFile.	IField
NamedBlobImage	NamedBlobImage	A binary uploaded image stored as a ZODB BLOB. Requires the [blobs] extra to plone.namedfile. Otherwise identical to NamedImage.	IField

Fields in z3c.relationfield.schema

See z3c.relationfield for more details

Name	Type	Description	Properties
Relation	RelationValue	Stores a single RelationValue.	IField
RelationList	list	A List field that defaults to Relation as the value type	See List
RelationChoice	RelationValue	A Choice field intended to store RelationValue's	See Choice

Fields in plone.app.textfield

See plone.app.textfield for more details

Name	Type	Description	Properties
RichText	RichTextValue	Stores a RichTextValue, which encapsulates a raw text value, the source MIME type, and a cached copy of the raw text transformed to the default output MIME type.	IField, IRichText