如何基于表格中的数据在Django表单上显示项目？

Question

I am trying to figure out how to display a form based on data from a table. I basically want to use the data from one table as a label to enter data that goes into another table.

I have two food tables:

class FoodType(models.Model):
  name = models.CharField(max_length=200)

class Food(models.Model):
  foodtype = models.ForeignKey(FoodType)
  tracktemp = models.BooleanField(verbose_name="Track Temperature?")

and a Temp table like this:

class Temp(models.Model):
  date = models.DateField('Entry Date')
  time = models.TimeField('Entry Time')
  food = models.ForeignKey(Food)
  temp = models.IntegerField(max_length=4, blank=True, null=True)

I have two foods in my Food table (Beans, Sprouts) and tracktemp is set to True for each of them.

In the Temp table I want to be able to add multiple records, each of which has a single temp at a particular time. For example:

Beans  1st Dec 2012 6.00pm     230
Beans  1st Dec 2012 6.04pm     235
Beans  1st Dec 2012 6.10pm     240

To do this I want to be able to render a form like this to enter the temps:

Beans   [    ]
Sprouts [    ]
[save]

Some notes about the above form:

• The food names should be labels, not combo boxes.
• I will not show the date/time fields and just programmatically set them.

As such I need to find all items in the Food table that have tracktemp set to 'True' and use that to present a form to the user so the user can add a temp for that time.

How can I do this?

Answer 1

The tricky part is basically the rendering of the Temp.food as something other than a select widget(which is the default for ForeignKey relationships).

For this you'd have to subclass the Select widget and override the render method to output just a label with the selected value

from django.forms.widgets import Select

class MyLabelSelect(Select):
    def render(self, name, value, attrs=None, choices=()):
        # read the django.forms.widgets.Select.render() source to 
        # understand what you have to do here. Not that hard.
        pass

A formset is indeed what you need here, with a caveat: you'll need to pass it a slightly custom form that uses your new widget for the FK relationship.

from django import forms
from .widgets import MyLabelSelect
from .models import Temp

class TempForm(forms.ModelForm):
    class Meta:
        model = Temp
        exclude = ('date', 'time')
        widgets = {
            'food': MyLabelSelect
        }

OK now we need to construct the actual formset

from django.forms.models import modelformset_factory
from .forms import TempForm
from .models import Temp

def my_view(request):
    TempFormset = modelformset_factory(
        Temp,
        form = TempForm,
        max_num = Temp.objects.count()
    )

    if request.method == 'POST' and request.POST:
        # I'll just demonstrate the GET request
        pass
    else:
        # Grab the Temp objects we want
        temps = Temp.objects.filter(food__tracktemp=True)
        temp_formset = TempFormset(
            queryset=temps 
        )
    return render_to_response(....)

Haven't actually tested the above code, but something along those lines is what you're after. If I have any glaring errors tell me and I'll correct them.