2. Objectives
Explore Django forms API
Review the Django forms documentation
Create forms using the Django Forms API
3. Out of the Box
Form handling django library
Automatically displays HTML form elements
Validates submitted data
Displays validation errors
Automatically converts submitted data into relevant data
types.
5. forms.py
Forms are composed of fields
from django import forms
class ContactForm(forms.Form):
name = forms.CharField()
email = forms.EmailField()
age = forms.IntegerField()
6. forms.py - fields
Each field has custom validation logic and other useful hooks.
name = forms.CharField(
label =“Full Name”,
max_length = “50”,
)
email = forms.EmailField(
max_length = “100”,
required = “false”
)
age = forms.IntegerField(
min_value = 18,
)
7. forms.py - widgets
Each field has a default widget which serves to render html.
name = forms.CharField(
label =“Full Name”,
max_length = “50”,
widget = forms.TextInput(
attrs = { „size‟ : ‟50‟, „class‟ = „customClass‟ }
)
)
email = forms.EmailField(
max_length = “100”,
required = “false”,
widget = forms.HiddenInput()
)
age = forms.IntegerField(
min_value = 18,
widget = forms.TextInput()
error_messages={‟invalid': ‟Only numbers please.'}
)
8. Instantiation : Bound vs Unbound
Unbound forms don‟t have data associated with them, but then
can be rendered.
form = ContactForm()
Bound forms have specific data associated, which can be
validated.
form = ContactForm(data = dataDict)
9. Initial Data
Data displayed only in unbound forms, and are not used as
fallback values if a particular value isn‟t provided.
Initial != Default
Can be set two different ways :
1. Set it in the field declaration of your form.
age = forms.IntegerField(initial=18)
2. Set it when you instantiate your form.
form = ContactForm(initial = initialDict)
11. Form Validation Overview
Only bound forms may be validated
Validation is triggered when form.is_valid() is called
Validated, cleaned data is stored in form.cleaned_data
Perform the full validation cycle by calling form.full_clean()
12. Field Validating
Three phases for fields: To Python, Validation, and Cleaning
If validation raises an Error, cleaning is skipped
Validators are callables that can raise a ValidationError
Django inlcludes generic ones for common tasks.
URLS, Min/Max Value, Email, etc.
13. Validators - defining
A callable that takes a value and raises a ValidationError; can
be useful for reusing validation logic.
App/validators.py
from django.core.exceptions import ValidationError
Import re
def validate_full_name(value):
if len(re.findall(r'w+', value)) < 2:
raise ValidationError(u‟%s is not a full name.‟ % value)
14. Validators - using
from django import forms
from projectgroup.project.application.validators import validate_full_name
class ContactForm(forms.Form):
name = forms.CharField(
label =“Full Name”,
max_length = “50”,
validators = [validate_full_name]
)
email = forms.EmailField(
max_length = “100”,
required = “false”
)
age = forms.IntegerField(
min_value = 18,
)
15. Field Cleaning
.clean_fieldname() is called after validators
Input has already been converted to Python objects
Methods can still raise ValidationError
Methods must return the cleaned_value
16. Specific Field Cleaning Example
from django import forms
from projectgroup.project.application.validators import validate_full_name
class ContactForm(forms.Form):
# Everything as before
…
def clean_email(self):
data = self.cleaned_data.get(„email‟, „‟)
if „gmail.com‟ not in data:
raise forms.ValidationError(“Why you no like gmail?”)
# always return the cleaned data, whether you have change
# it or not
return data
17. Form Validation
.clean() perform cross-field validation
Called even if errors were raised by Fields
Must return the cleaned data dictionary
ValidationError‟s raised by .clean() will be grouped in
form.non_field_errors() by default
18. Cross-field Cleaning Example
from django import forms
from projectgroup.project.application.validators import validate_full_name
class ContactForm(forms.Form):
# Everything as before
…
def clean (self):
cleaned_data = super(ContactForm, self).clean()
age = cleaned_data.get(“age”)
email = cleaned_data.get(“email”)
if not age and not email:
raise forms.ValidationError(“Age and email are required.”)
return cleaned_data
22. Dynamically Created
<form id=“contact” action=“” method=“get”>
{{ form.as_p }}
<input type=“submit” name=“save”/>
</form>
<form id=“contact” action=“” method=“get”>
{{ field.non_form_errors }}
{% for field in form %}
<div class=“fieldWrapper”>
{{ field.errors }}
{{ field.label_tag }}: {{ field }}
</div>
{% endfor %}
<input type=“submit” name=“save”/>
</form>
23. Model Forms
modelForms map a model to a form
validation includes model validators
Supports creating and editing instances
Key differences from forms
There will be a field for a primary key (id)
New save() method
New instance attribute
24. Model Form Example
app/models.py
from django import models
class Contact(models.Model):
name = models.CharField(max_length=50)
email = models.EmailField()
age = models.IntegerField()
app/forms.py
from django import forms
from grp.prj.app.models import Contact
class ContactForm(forms.Modelform):
class Meta:
model = Contact
25. Limiting Fields
Specify fields to expose, or fields to exclude
app/forms.py
from django import forms
from grp.prj.app.models import Contact
class ContactForm(forms.ModelForm):
class Meta:
model = Contact
fields = ('name', 'email',)
class ContactForm(forms.ModelForm):
class Meta:
model = Contact
exclude = (‟age',)
26. Instantiating Model Forms
Like before, we may have bound and unbound Model Forms
Unbound
mform = ContactForm()
Bound
mform = ContactForm(instance=Contact.objects.get(id=2) )
27. Handling forms in views.py
1. Import your form(s)
2. Within your view function
1. Check for submission(GET or POST).
1. If submitted
1. bind the form to the data.
2. Validate.
1. If its valid, do stuff.
2. Otherwise let it remain unbound.
3. Pass form to the context
4. Render your page.
28. views.py example
from grp.prj.app.forms import ContactForm
…
def contactView(request):
context = {}
contactPDA = Dpdpcntc()
…
initials = {
‘age' : ’18'
}
#instantiate
if request.GET.get(„submit‟):
form = ContactForm(data = request.GET)
if form.is_valid():
….
else:
form = ContactForm(initial=initials)
context[„form‟] = form
return render_to_response(…)
Import Form
Check for submission
Bind Form
Form Validation
Unbound Form
Render HTML
Form in Context
29. views.py – other examples
if request.GET.get(„submit‟):
form = ContactForm(request.GET)
if form.is_valid():
….
else:
form = ContactForm(initial=initials)
if request.GET:
form = ContactForm(request.GET)
if form.is_valid():
….
else:
form = ContactForm(initial=initials)
form = ContactForm(data=request.GET or None, initial=initials)
if form.is_valid():
….