CompoundField and ArrayField

Prerequisites

Install the "CompoundField":http://plone.org/products/compoundfield extension
into you Products folder.

List of fields - ArrayField

Assume you want to have content type where the user can provide one or more files.
Its easy by making the type folderish. But for some use-cases this is to heavy or to
difficult, you want the user to use a form for those files.

You could say, ok, up to 5 files is enough and model 5 file fields into your class.
Not very elegant, huh?

The easiest way is to to use the UML 'multiplicity' feature on your attribute aka field of the
class. If you want to enable unlimited attachments use multiplicity '*'.
Or choose a number like '5', as in our above example.

You can set the initial size of the array by using the tagged value 'array:size' to 'python:10' for example.
Prefixed with 'array:' you can access also the label 'array:widget:label' of it and so on.
If you prefer the EnhancedArrayWidget you need to add an tagged value 'imports'
'from Products.Compoundfield.EnhancedArrayWidget import EnhancedArrayWidget' to your class
and set on the attribute the tagged value 'array:widget:type' to 'EnhanceArrayWidget'.

Custom Fields compounds - CompoundField

With ArchGenXML you can create compounds of fields from existing fields.
Such a set of fields behaves almost like a normal field.
To create such a compounded field create a new class and give it the
stereotype '<<field>&gt'

Now add attributes to it like you would do on a content type class.
You can use almost every field type, just some special fields, mostyl those
acting as a proxy without own storage, wont work (such as ReferenceField or AttachementField).

For example we create a 'PointField' consisting out of two 'FloatFields' by
just adding a 'x' and 'y' attribute of type 'float'.

To use the new field create a fresh content class and name it 'Polygon'.
Take a dependency arrow pointing from your Polygon class to the field class.
This ensures it gets imported!

Next add an attribute 'points' to the class. The type of the new points attribute
is 'PointsField'. Now to make it a polygon give it a multiplicity of *and
your done: You have a list of Points as one field.