How to restrict a record field to one sample type#

This guide keeps a sample field to the samples of one registered type. You would do this on a form that must refer to, say, a core sample and never to a water sample.

Before you start#

You need a registered sample type. This guide uses CoreSample, a sample type of your portal. To add one, see How to add a sample type.

Steps#

Import the sample field and your sample model.

from fairdm.contrib.autocomplete.fields import SampleChoiceField
from myportal.models import CoreSample

Pass the model as type.

from django import forms


class CompareCoresForm(forms.Form):
    core_sample = SampleChoiceField(type=CoreSample)

Build the form inside a request, as in How to add a record field to a form.
```
form = CompareCoresForm(request.POST or None)
```

The result#

The field offers core samples only, found by name, local ID or identifier. A sample of any other type is refused with invalid_choice when the form is saved, even if the browser sent its key.

type must be a subclass of the kind’s model. A project or dataset field, or a model of another kind, raises ValueError when the field is created. The multiple field takes type in the same way.