[Django]-Tutorial about how to write custom form fields in django?

by

34👍

✅

Form fields are easy to customize:

class UpperCaseField(forms.CharField):
    def clean(self, value)
        try:
            return value.upper()
        except:
            raise ValidationError

basically you just create a class that inherits from the field that most resembles what you want, then rewrite the clean() method so that it returns the value you want. Here is another example:

class MyObjectField(forms.ModelChoiceField):
    # in this case, 'value' is a string representing
    # the primary key of a MyObject
    def clean(self, value):
        try:
            return MyObject.objects.get(pk=value)
        except:
            raise ValidationError

custom widgets on the other hand, are a little more useful, but a little more hard to do because there are a few more methods that need to be written so that they work smoothly.

👤priestc

17👍

As always with open-source code, you’ll learn a great deal by reading the source itself. See the django.forms.fields module to see how all the different form fields are defined – most of them are subclasses of others already, so you can just replicate that and change what you need.

👤Daniel Roseman

6👍

It’s not a tutorial, but django’s docs talks about this a little:

If the built-in Field classes don’t
meet your needs, you can easily create
custom Field classes. To do this, just
create a subclass of
django.forms.Field. Its only
requirements are that it implement a
clean() method and that its __init__()
method accept the core arguments
mentioned above (required, label,
initial, widget, help_text).

You can read about the clean method and see an example at the django docs. Again, not a tutorial, but useful.

I find I am learning a lot by reading the code in some of the the django app projects that are available, such as django-extensions, which override the form fields and are good learning tools (for me, at least). This can help get you started.

👤thornomad

0👍

I found these tutorials helpful:

As you have already mentioned, the Django documentation has a section How to create custom model fields which unfortunalety deals only with model fields, and moreover, it is not very comprehensive.

As Daniel already recommended, you can read throught the source code of the django.forms.fields module to see how all the different form fields are defined, and this might help you learn how to define new ones.

You can also learn a lot from custom form field examples here on Stack Overflow, such as Custom hidden field, Custom password field, Custom form field, and Custom tag field.

Note: I have added all good resources that I know of, if someone knows about other. Please let me know in the comments and I will add them.

👤Jakub Holan

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