Custom form field

[Daniel Gagnon]

I'm trying to create a custom form field and I'm not succeeding at it so far.

I want to create an autocomplete field with jquery. It would be used on models that refer another model via a foreign key where the linked model have an id and a name (unique). I would like to render the name of the linked model in html. I would like the user to be able to select a value via autocompletion (possibly thousands of values). And I would like the to_python to query the db to get the actual object associated with the name the user picked via autocompletion.

The javascript part of the equation works very well. However, I'm having trouble with the creating a custom field part. I wasted a few hours on this so far and I'm just not getting how to do it.

Could someone give me some pointers on this?

Thanks

[Shawn Milochik]

Maybe just save your time and re-use some tasty open-source.

Examples:

http://code.google.com/p/django-ajax-selects/

http://code.google.com/p/django-autocomplete/

[Daniel Gagnon]

The first one uses a jquery plugin that's discontinued and the second one works only in the admin.

Also, I feel I'm missing something that's not so complex...

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[Shawn Milochik]

http://docs.djangoproject.com/en/1.3/howto/custom-model-fields/

What specific problems/errors are you experiencing?

[Daniel Gagnon]

I'm trying to create a Form Field, not a Model Field.

The doc about creating a custom one is a tiny paragraph at the end of this page: http://docs.djangoproject.com/en/1.3/ref/forms/fields/

I read the source code of django but I'm having trouble even finding where exactly is the value stored in the field.

The problems I have are that I don't know how to do the following:

• The field is going to receive an object and should render the name property of that object in html (so far, I can only render the id).
• The page is going to POST a string containing the name of the object (unique), it should be converted back to an object.

On Wed, Apr 20, 2011 at 11:11 AM, Shawn Milochik <sh...@milochik.com> wrote:

http://docs.djangoproject.com/en/1.3/howto/custom-model-fields/

What specific problems/errors are you experiencing?

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[Daniel Roseman]

On Wednesday, April 20, 2011 4:20:04 PM UTC+1, Dan wrote:

I'm trying to create a Form Field, not a Model Field.

The doc about creating a custom one is a tiny paragraph at the end of this page: http://docs.djangoproject.com/en/1.3/ref/forms/fields/

I read the source code of django but I'm having trouble even finding where exactly is the value stored in the field.

The problems I have are that I don't know how to do the following:

• The field is going to receive an object and should render the name property of that object in html (so far, I can only render the id).
• The page is going to POST a string containing the name of the object (unique), it should be converted back to an object.

Rendering is the job of the widget, not the field. You will need to define a custom widget and make that the default for your field.

Converting a POSTed value is the job of the field's `clean()` method. 

--

DR.

[Daniel Gagnon]

So far, I have the following code:

from django.forms.widgets import TextInput

from django.forms.fields import Field

class AutoCompleteWidget(TextInput):

    def render(self, name, value, attrs=None):

        if hasattr(value, 'name'):

            v = value.name

        else:

            v = None

        super(AutoCompleteWidget, self).render(self, name, v, attrs)

class AutoCompleteField(Field):

    widget = AutoCompleteWidget

    def clean(self):

        pass    # Not implemented yet

class TicketForm(ModelForm):

    target = AutoCompleteField()

    class Meta:

        model = Ticket

        exclude = ('slug')

When I use this code the whole form stops rendering! What's wrong with my widget?

--

[DrBloodmoney]

On Wed, Apr 20, 2011 at 11:48 AM, Daniel Gagnon <redal...@gmail.com> wrote:
> So far, I have the following code:
> from django.forms.widgets import TextInput
> from django.forms.fields import Field
> class AutoCompleteWidget(TextInput):
>     def render(self, name, value, attrs=None):
>         if hasattr(value, 'name'):
>             v = value.name
>         else:
>             v = None
>         super(AutoCompleteWidget, self).render(self, name, v, attrs)
> class AutoCompleteField(Field):
>     widget = AutoCompleteWidget
>     def clean(self):
>         pass    # Not implemented yet
> class TicketForm(ModelForm):
>     target = AutoCompleteField()
>     class Meta:
>         model = Ticket
>         exclude = ('slug')
>
> When I use this code the whole form stops rendering! What's wrong with my
> widget?

Take out the self in the super call
(ie) Change this:

super(AutoCompleteWidget, self).render(self, name, v, attrs)

to this:

super(AutoCompleteWidget, self).render(name, v, attrs)

[Daniel Gagnon]

Thanks

It still doesn't work though. I found out through logging that value that is receive is an int (the id) instead of being the object itself. How can I make my widget pass the object itself to the widget instead of passing object.id ?

[DrBloodmoney]

Could you also include the model?

[Daniel Gagnon]

Sure, here's a minimal version of them (I skipped fields that aren't too relevant to the problem at hand because there's many, including tons of foreign keys):

class Target(Model):

    name = CharField("Target Name", max_length=255, unique=True)

    created = DateTimeField(auto_now_add=True, editable=False)

    modified = DateTimeField(auto_now=True, editable=False)

class Ticket(Model):

    target = ForeignKey(Target, related_name="tickets")

    reference = CharField(max_length=255)

    created = DateTimeField(auto_now_add=True, editable=False)

    modified = DateTimeField(auto_now=True, editable=False)

[DrBloodmoney]

On Wed, Apr 20, 2011 at 12:45 PM, Daniel Gagnon <redal...@gmail.com> wrote:
> Sure, here's a minimal version of them (I skipped fields that aren't too
> relevant to the problem at hand because there's many, including tons of
> foreign keys):
> class Target(Model):
>     name = CharField("Target Name", max_length=255, unique=True)
>     created = DateTimeField(auto_now_add=True, editable=False)
>     modified = DateTimeField(auto_now=True, editable=False)
> class Ticket(Model):
>     target = ForeignKey(Target, related_name="tickets")
>     reference = CharField(max_length=255)
>     created = DateTimeField(auto_now_add=True, editable=False)
>     modified = DateTimeField(auto_now=True, editable=False)

It probably is related to the this being a foreign key field and in
order for it to produce a valid object instance from the Target model,
it needs a queryset. Try to subclass from ModelChoiceField[1] and see
if that works.

[1] http://code.djangoproject.com/browser/django/trunk/django/forms/models.py#L891

[Daniel Gagnon]

New code:

 

from django.forms.widgets import Select

from django.forms.models import ModelChoiceField

from Server_Automation.target_mgmt.models import Target

class AutoCompleteWidget(Select):

    def render(self, name, value, attrs=None, choices=()):

        logger.debug(value)     # Logs 1 (the id)

        logger.debug(choices)   # Logs and empty tuple

        super(AutoCompleteWidget, self).render(name, value, choices)

class AutoCompleteField(ModelChoiceField):

    widget = AutoCompleteWidget

class TicketForm(ModelForm):

    target = AutoCompleteField(queryset=Target.objects.all())

    class Meta:

        model = Ticket

        exclude = ('slug',)

For a reason I ignore, my model just doesn't want to pass the choices to the widget and it takes the default value (an empty tuple). I verified this by changing the default value and checking the log.

[Daniel Gagnon]

It probably is related to the this being a foreign key field and in
order for it to produce a valid object instance from the Target model,
it needs a queryset. Try to subclass from ModelChoiceField[1] and see
if that works.

[1] http://code.djangoproject.com/browser/django/trunk/django/forms/models.py#L891

Code now:

from django.forms.widgets import Select

from django.forms.models import ModelChoiceField

from Server_Automation.target_mgmt.models import Target

class AutoCompleteWidget(Select):

    def render(self, name, value, attrs=None, choices=()):

        logger.debug(value)     # Logs 1 (the id)

        logger.debug(choices)   # Logs and empty tuple

        super(AutoCompleteWidget, self).render(name, value, choices)

class AutoCompleteField(ModelChoiceField):

    widget = AutoCompleteWidget

class TicketForm(ModelForm):

    target = AutoCompleteField(queryset=Target.objects.all())

    class Meta:

        model = Ticket

[Derek]

On Apr 20, 5:06 pm, Daniel Gagnon <redalas...@gmail.com> wrote:
"The first one uses a jquery plugin that's discontinued and the second
one
works only in the admin."

But that first project is live; did you contact the author and ask him/
her about plans to update it (especially as the jquery plugin in
question has a clear upgrade path)?

[Karen Tracey]

On Wed, Apr 20, 2011 at 11:06 AM, Daniel Gagnon <redal...@gmail.com> wrote:

The first one uses a jquery plugin that's discontinued and the second one works only in the admin.

There is also:

https://bitbucket.org/mlavin/django-selectable

Karen

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