Question

Is there a way in Django to add custom attributes to a model’s fields (without resorting to subclassing fields)?

I would like to only display certain fields in certain sections of my template. This is because eventually each type of field will be displayed in a separate tab. I thought about adding a custom attribute to each field to identify which section/tab it should go in. But, so far, I’ve had no luck.

I have a few field types:

class Enum(set):
    def __getattr__(self, name):
        if name in self:
            return name
        raise AttributeError

FieldTypes = Enum(["one","two","three",])

And a few models:

class Model1(models.Model):
  a = models.CharField()
  b = models.ForeignKey('Model2')
  c = models.IntegerField()
  a.type = FieldTypes.one  # this obviously doesn't work
  b.type = FieldTypes.two  # this obviously doesn't work
  c.type = FieldTypes.three  # this obviously doesn't work

class Model2(models.Model):
  d = models.CharField()

And a form:

class Form1(forms.ModelForm):
  class Meta:
    model = Mode1

And a template:

{% for fieldType in FieldTypes %}
  <div class="{{fieldType}}">
      {% for field in form %}
        {% if field.type = fieldType %}
          {{ field }}
         {% endif %}
      {% endfor %} 
  </div>
{% endfor %}

But this doesn’t work.

Ideas? Or other suggestions for only placing certain fields in certain sections of the page?

Thanks.

Answer 1

In general, I would keep this logic outside of the model class. Models shouldn’t be tangled up with presentation elements if you can help it, and choosing which fields to display in a form seems like a presentation concern. Fortunately, the Form class provides a nice, UI-focused layer between the data layer (the model) and the presentation layer (the view and template).

Here’s how I’ve addressed this in the past. In my Form class, I created a list of field groups, each with a title and a list of the names of the fields they contain:

class MyModelForm(forms.ModelForm):
    field_groups = (
        {'name':'Group One', 'fields':('a', 'b', 'c')},
        {'name':'Group Two', 'fields':('d', 'e')},
    )
    class Meta:
        model = MyModel

Then in the template, I looped through the groups, and within that loop conditionally included those fields:

{% for group in form.field_groups %}
<h3 class="groupheader">{{group.name}}</h3>
    {% for field in form %}
        {% if field.name in group.fields %}
        <div class="fieldWrapper">
            {{ field.errors }}
            {{ field.label_tag }}: {{ field }}
        </div>
        {% endif %}
    {% endfor %}
{% endfor %}

This allows you to control the grouping and display of form fields within the MyModelForm class, which is a reasonable place for presentation logic to live.