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Django - ModelForm

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• Django - ModelForm
  • ModelForm
    • Example: Create Form class from model
  • Field types
  • save() method
  • Meta Class

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ModelForm

• ModelForm
  • a class which is used to create an HTML form by using the Model.
  • an efficient way to create a form without writing HTML code.
• Meta
  • an inner class provides information connecting the model to the form.
• Syntax:

  class Model_Form(ModelForm):
    # some form fields
    class Meta:
        model = model_name
        fiels = []
        # some info about this form, such as help_texts ro widgets
  

Example: Create Form class from model

• Example:

from django.forms import ModelForm
from myapp.models import Article

# Create the form class.
class ArticleForm(ModelForm):
    class Meta:
        model = Article
        fields = ["pub_date", "headline", "content", "reporter"]

# Creating a form to add an article.
form = ArticleForm()

# Creating a form to change an existing article.
article = Article.objects.get(pk=1)
form = ArticleForm(instance=article)

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Field types

• Auto ID

Model field	Form field
AutoField	Not represented in the form
BigAutoField	Not represented in the form
SmallAutoField	Not represented in the form

• Number

Model field	Form field
BooleanField	BooleanField, or NullBooleanField
IntegerField	IntegerField
PositiveIntegerField	IntegerField
BigIntegerField	IntegerField
PositiveBigIntegerField	IntegerField
SmallIntegerField	IntegerField
PositiveSmallIntegerField	IntegerField
FloatField	FloatField

• String

Model field	Form field
BinaryField	CharField
CharField	CharField
EmailField	EmailField
FilePathField	FilePathField
IPAddressField	IPAddressField
GenericIPAddressField	GenericIPAddressField
JSONField	JSONField
SlugField	SlugField
TextField	CharField with widget=forms.Textarea
URLField	URLField
UUIDField	UUIDField

• Date

Model field	Form field
DateField	DateField
DateTimeField	DateTimeField
DecimalField	DecimalField
DurationField	DurationField
TimeField	TimeField

• File

Model field	Form field
FileField	FileField
ImageField	ImageField

• Relationship

Model field	Form field
ForeignKey	ModelChoiceField
ManyToManyField	ModelMultipleChoiceField

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save() method

• Example: Create and update

from myapp.models import Article
from myapp.forms import ArticleForm

# Create a form instance from POST data.
f = ArticleForm(request.POST)

# Save a new Article object from the form's data.
new_article = f.save()

# Create a form to edit an existing Article, but use
# POST data to populate the form.
a = Article.objects.get(pk=1)
f = ArticleForm(request.POST, instance=a)
f.save()    # update

• Example: save the many-to-many form data

# Create a form instance with POST data.
f = AuthorForm(request.POST)

# Create, but don't save the new author instance.
new_author = f.save(commit=False)

# Modify the author in some way.
new_author.some_field = "some_value"

# Save the new instance.
new_author.save()

# Now, save the many-to-many data for the form.
f.save_m2m()

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Meta Class

Attributes	Description
model	the model to refer to
fields	the fields used in the form. __all__: all fields
exclude	fields to be excluded
widgets	a dictionary mapping field names to widget
labels	a dictionary mapping field names to label tag
help_texts	a dictionary mapping field names to help_texts
error_messages	a dictionary mapping field names to errors
field_classes	a dictionary mapping field names to type of fields
localized_fields	a list of field names to localize data

from django.utils.translation import gettext_lazy as _

class AuthorForm(ModelForm):
    class Meta:
        model = Author
        fields = ["name", "title", "birth_date"]
        labels = {
            "name": _("Writer"),
        }
        help_texts = {
            "name": _("Some useful help text."),
        }
        error_messages = {
            "name": {
                "max_length": _("This writer's name is too long."),
            },
        }

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