A developer dealing with Deform has to understand a few fundamental types of objects and their relationships to one another. These types are:
- schema nodes
- field objects
The Relationship Between Widgets, Fields, and Schema Objects
The relationship between widgets, fields, and schema node objects is as follows:
- A schema is created by a developer. It is a collection of :term:`schema node` objects.
- When a root schema node is passed to the :class:`deform.Form` constructor, the result is a :term:`field` object. For each node defined by the developer in the schema recursively, a corresponding :term:`field` is created.
- Each field in the resulting field tree has a default widget type.
widgetattribute of a field object is not set directly by the developer, a property is used to create an instance of the default widget type when
field.widgetis first requested. Sane defaults for each schema type typically exist; if a sane default cannot be found, the :class:`deform.widget.TextInputWidget` widget is used.
The Colander documentation is a resource useful to Deform developers. In particular, it details how a :term:`schema` is created and used. Deform schemas are Colander schemas. The Colander documentation about how they work applies to creating Deform schemas as well.
A widget is related to one or more :term:`schema node` type objects. For example, a notional "TextInputWidget" may be responsible for serializing textual data related to a schema node which has :class:`colander.String` as its type into a text input control, while a notional "MappingWidget" might be responsible for serializing a :class:`colander.Mapping` object into a sequence of controls. In both cases, the data type being serialized is related to the schema node type to which the widget is related.
field object (``field``) | | |----- widget object (``field.widget``) | | \----- schema node object (``field.schema``)