Websauna comes with special Deform form widget support, mainly to deal with SQLAlchemy models. For complete Deform built-in widget reference see Deform demo site.

SQLAlchemy widgets

Choose one instance

Use websauna.system.form.sqlalchemy.ForeignKeyValue and websauna.system.form.sqlalchemy.UUIDForeignKeyValue.

An example below. websauna.system.form.fields.defer_widget_values() is used to lazily populate value list during the run-time.

import colander
import deform
import deform.widget
from websauna.system.form.schema import CSRFSchema
from websauna.utils.slug import uuid_to_slug
from websauna.system.form.sqlalchemy import UUIDForeignKeyValue
from websauna.system.form.fields import defer_widget_values

def available_networks(node: colander.SchemaNode, kw: dict) -> list:
    """Create """
    request = kw["request"]
    query = request.dbsession.query(AssetNetwork).all()
    return [(uuid_to_slug(network.id), network.name) for network in query]

class MoveNetworkSchema(CSRFSchema):

    #: Choose network there this item belongs to
    network = colander.SchemaNode(
        UUIDForeignKeyValue(model=AssetNetwork, match_column="id"),
        widget=defer_widget_values(deform.widget.SelectWidget, available_networks),

# Ten some example view

@view_config(context=AssetDescription, route_name="network", name="move", permission="manage-content", renderer="network/rename.html")
def move(asset_desc: AssetDescription, request: Request):
    """Rename asset.

    Allow change it title and symbol, but optionally keep slug intact.

    schema = MoveNetworkSchema().bind(request=request)
    asset = asset_desc.asset  # type: websauna.wallet.models.Asset

    # ...

    # User submitted this form
    if request.method == "POST":

            appstruct = form.validate(request.POST.items())

            # We get direct SQLAlchemy reference here
            asset.network = appstruct["network"]

        except deform.ValidationFailure as e:
            # Render a form version where errors are visible next to the fields,
            # and the submitted values are posted back
            rendered_form = e.render()

        # Populate default values
        appstruct = {
            "network": asset.network,
        # Render a form with initial values
        rendered_form = form.render(appstruct=appstruct)

    return locals()