How to override admin field widget?

Mark Phillips

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Apr 11, 2014, 1:56:42 AM4/11/14

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I hope I am using the right terminology....

I have a Decimal field in a model called 'width'. In the admin screen, I would like to display this field as three text boxes like this:

width: [] []/[]

so I can enter 2 1/8 for the width, and then have the code convert that to 2.125 as a Decimal field and store that Decimal field in the database.

How would I go about doing this?

Thanks,

Mark

Lucas Klassmann

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Apr 11, 2014, 2:09:42 AM4/11/14

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Hi!

I never used this, but i found here and can be useful:

https://docs.djangoproject.com/en/dev/ref/forms/widgets/#django.forms.MultiWidget

Cheers.

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Mark Phillips

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Apr 11, 2014, 2:25:06 PM4/11/14

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I looked at the MultiWidget and tried to implement following a couple of examples, but I have run into a problem. I get this error when I try to open the admin form - type object 'MeasurementWidget' has no attribute 'attrs'

widgets.py

class MeasurementWidget(forms.MultiWidget):

def __init__(self, attrs=None):

widgets = (

forms.textInput(attrs=attrs),

)

super(MeasurementWidget, self).__init__(widgets, attrs)

def decompress(self, value):

if value:

frac = Fraction(value)

num = frac.numerator

denom = frac.denominator

whole = num/denom

if whole == 0:

whole = ''

numerator = num - (num/denom)*denom

return [whole, numerator, denom]

return ['', '', '']

def format_output(self, rendered_widgets):

return u''.join(rendered_widgets)

def value_from_datadict(self, data, files, name):

valuelist = [widget.value_from_datadict(data, files, name + '_%s' % i) for i, widget in enumerate(self.widgets)]

try:

if valuelist[0] == '':

valuelist[0] = 0

numerator = int(valuelist[0]) * int(valuelist[2]) + int(valuelist[1])

denominator = int(valuelist[2])

return Decimal(float(Fraction(numerator, denominator)))

except ValueError:

return ""

models.py

class Inventory(models.Model):

location = models.ForeignKey(Location)

room = models.ForeignKey(Room, blank=True, null=True)

condition = models.ForeignKey(Condition)

status = models.ForeignKey(Status)

category = models.ForeignKey(Category)

length = models.DecimalField(max_digits=5, decimal_places=3, default=0)

width = models.DecimalField(max_digits=5, decimal_places=3, default=0)

height = models.DecimalField(max_digits=5, decimal_places=3, default=0)

and other fields.....

admin.py

class MeasurementForm(forms.ModelForm):

def __init__(self, *args, **kwargs):

super(MeasurementForm, self).__init__(*args, **kwargs)

self.fields['width'].widget = MeasurementWidget

self.fields['height'].widget = MeasurementWidget

self.fields['length'].widget = MeasurementWidget

class Meta:

model = Inventory

class InventoryAdmin(admin.ModelAdmin):

list_display = ('id','location', 'room', 'category', 'description', 'condition', 'length', 'width', 'height', 'status', 'sale_price', 'selling_costs', 'debt')

list_filter = ['category']

search_fields = ['description']

form = MeasurementForm

inlines = [NoteInline, ImageInline, EstimateInline]

admin.site.register(Inventory, InventoryAdmin)

I am really lost here. Does anyone have an easier way to override the widgets on the admin form?

Thanks,

Mark

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Lucas Klassmann

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Apr 11, 2014, 2:37:05 PM4/11/14

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Hi!

I will test you code, but for now, try rewrite the form class, this way:

class MeasurementForm(forms.ModelForm):

width = forms.DecimalField(widget=MeasurementWidget())

height = forms.DecimalField(widget=MeasurementWidget())

length = forms.DecimalField(widget=MeasurementWidget())

class Meta:

model = Inventory

Cheers.

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Mark Phillips

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Apr 11, 2014, 2:59:48 PM4/11/14

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Lucas,

Thanks for your comment.

I tried your suggestion, and got this error

'module' object has no attribute 'textInput'

referring to the forms.textInput(attrs=attrs) in the widget class.

I am only trying to replace three out of 16 fields in my Inventory model with the custom widgets. I think your solution would require me to enumerate all the other fields as well? I found this on the Internet - http://collingrady.wordpress.com/2008/07/24/useful-form-tricks-in-django/, which gave me the idea for how I wrote the form.

I could be totally off base, so this is a great learning experience for me! Thanks for your help!

Mark

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Lucas Klassmann

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Apr 11, 2014, 3:05:36 PM4/11/14

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Hi Mark,

Because TextInput is a classe inside forms module and python is case-sensitive, try this:

forms.TextInput(attrs=attrs)

Cheers.

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Mark Phillips

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Apr 11, 2014, 3:33:03 PM4/11/14

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Man, are you good....;)

It now works as expected!

One last question....the form shows three text boxes next to each other. How can I change the html to look like this:

[ ] [ ] / [ ]

{text_box} space {text_box} / {text_box}

It has something to do with format_output, but I don't understand how to return a string to represent this layout. Also, how to control the size of the text boxes.

Thanks again!!

Mark

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Lucas Klassmann

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Apr 11, 2014, 4:03:43 PM4/11/14

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Hi Mark,

You must understand that each Widget in :

widgets = (

forms.TextInput(attrs=attrs),

)

Has a render() method that return html of widget. You must only concatenate each html of widget. You can use format_output like this:

def format_output(self, rendered_widgets):

widget_a = rendered_widgets[0]

widget_b = rendered_widgets[1]

widget_c = rendered_widgets[2]

return "%s %s/%s" $(widget_a, widget_b, widget_c)

I hope that solution above be that you want, but if you want customizing html/css/javascript of TextInput widget, you must override render() method of forms.TextInput widget.

Cheers.

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Mark Phillips

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Apr 11, 2014, 4:13:40 PM4/11/14

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Ahhhh....that makes sense.

I was able to change the size of the text box in the widget file this way...

forms.TextInput(attrs={'size':'5'}),

Thanks again for all your help!! I learned a lot!

Mark

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