Deform Components

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
  • widgets

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 schema node objects.
  • When a root schema node is passed to the deform.Form constructor, the result is a field object. For each node defined by the developer in the schema recursively, a corresponding field is created.
  • Each field in the resulting field tree has a default widget type. If the widget attribute 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.widget is first requested. Sane defaults for each schema type typically exist. If a sane default cannot be found, the deform.widget.TextInputWidget widget is used.


The Colander documentation is a resource useful to Deform developers. In particular, it details how a 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 schema node type objects. For example, a notional "TextInputWidget" may be responsible for serializing textual data related to a schema node which has colander.String as its type into a text input control, while a notional "MappingWidget" might be responsible for serializing a 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.

A widget has a relationship to a schema node via a field object. A field object has a reference to both a widget and a schema node. These relationships look like the following.

field object (``field``)
     |----- widget object  (``field.widget``)
     \----- schema node object (``field.schema``)