Read-only form field formatting

I want to display a field as read only in a ModelAdmin form, so I added it to the readonly_fields attribute.

However, since the field contains a currency, stored as an integer, I want to apply some nice formatting it. I've created a custom ModelForm for my ModelAdmin, trying to apply the formatting in the overridden __init__ method.

The problem is, I cannot find the value. The field is not present in the self.fields attribute.

Does anyone know where the values for the readonly_fields are kept, or is there a better/different approach?

Answers

Just do something like:

class MyAdmin(admin.ModelAdmin):
    readonly_fields = ('foo',)

    def foo(self, obj):
        return '${0}'.format(obj.amount)

An alternate approach, which works for all types of forms is to create a widget to represent a read only field. Here is one that I wrote for my own use. You can change the <span %s>%s</span> to suit your own requirements.

from django import forms
from django.utils.safestring import mark_safe
from django.utils.encoding import force_unicode


class ReadOnlyWidget(forms.TextInput):
    def render(self, name, value, attrs=None):
         if value is None:
             value = ''
         final_attrs = self.build_attrs(attrs, type=self.input_type, name=name)
         if value != '':
             # Only add the 'value' attribute if a value is non-empty.
             final_attrs['value'] = force_unicode(self._format_value(value))
         return mark_safe(u'<span%s />%s</span>' % (flatatt(final_attrs),value))

Once you have that added, simply do this:

class MyAdmin(admin.ModelAdmin):
    foo = models.TextField(widget=ReadOnlyWidget(attrs={'class':'read-only'}
                           initial="$50")

Then in your CSS, do some styling for a read-only class, or you can adjust the attributes accordingly.

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