Form Utilities¶

Reusable base form classes and utilities for common validation patterns.

Overview¶

The forms module provides:

Abstract base form classes for common patterns
Form utilities for field manipulation and error handling
Integration with model forms
Helper functions for form processing

Base Form Classes¶

AbstractModelInstanceUpdateForm¶

Base class for forms that update model instances:

from htk.forms.classes import AbstractModelInstanceUpdateForm

class UserProfileForm(AbstractModelInstanceUpdateForm):
    class Meta:
        model = UserProfile
        fields = ['bio', 'website', 'location']

Features: - Automatic model instance update - Consistent error handling - Field validation and cleaning

Form Utilities¶

Field Input Attributes¶

Set attributes on form input fields:

from htk.forms.utils import set_input_attrs, set_input_placeholder_labels

# Set custom attributes
set_input_attrs(form, {'class': 'form-control', 'data-type': 'email'})

# Auto-populate placeholder with label
set_input_placeholder_labels(form)

Error Handling¶

from htk.forms.utils import get_form_errors, get_form_error

# Get all errors
all_errors = get_form_errors(form)  # List of all error messages

# Get first error
first_error = get_form_error(form)  # Single error string

Model Instance Validation¶

from htk.forms.utils import clean_model_instance_field

# Validate a field against model constraints
value = clean_model_instance_field(model_instance, field_name, value)

Common Patterns¶

Custom Form with Validation¶

from django import forms
from htk.forms.classes import AbstractModelInstanceUpdateForm

class RegistrationForm(AbstractModelInstanceUpdateForm):
    password = forms.CharField(widget=forms.PasswordInput)
    password_confirm = forms.CharField(widget=forms.PasswordInput)

    class Meta:
        model = User
        fields = ['username', 'email', 'password']

    def clean(self):
        cleaned_data = super().clean()
        password = cleaned_data.get('password')
        password_confirm = cleaned_data.get('password_confirm')

        if password != password_confirm:
            raise forms.ValidationError('Passwords do not match')

        return cleaned_data

    def save(self, commit=True):
        user = super().save(commit=False)
        user.set_password(self.cleaned_data['password'])
        if commit:
            user.save()
        return user

API Form Handling¶

from django.http import JsonResponse
from htk.api.utils import json_response_form_error

def api_update_user(request):
    form = UserUpdateForm(request.POST, instance=request.user)
    if form.is_valid():
        form.save()
        return JsonResponse({'success': True})
    else:
        return json_response_form_error(form)

Dynamic Field Rendering¶

from htk.forms.utils import set_input_attrs

def render_form(form, css_class='form-control'):
    set_input_attrs(form, {'class': css_class})
    set_input_placeholder_labels(form)
    return form

Integration with Models¶

Inherit from Abstract Models¶

from htk.apps.accounts.models import BaseAbstractUserProfile

class CustomUserProfile(BaseAbstractUserProfile):
    department = models.CharField(max_length=100)

class UserProfileForm(AbstractModelInstanceUpdateForm):
    class Meta:
        model = CustomUserProfile
        fields = ['bio', 'website', 'department']

Best Practices¶

Extend AbstractModelInstanceUpdateForm for model-related forms
Use field validators for single field validation
Override clean() for cross-field validation
Set input attrs early in form initialization
Return JSON errors in API views with json_response_form_error

Classes¶

AbstractModelInstanceUpdateForm - Base class for model update forms

Functions¶

save - Save form data to model instance
clean_model_instance_field - Validate field against model
set_input_attrs - Set HTML attributes on form fields
set_input_placeholder_labels - Auto-populate field placeholders
get_form_errors - Get all form errors as list
get_form_error - Get first form error as string