起步
Django 表单中有两种字段类型可以使用选择框: ChoiceField 和 ModelChoiceField 。
对于 ChoiceField 的基本使用是:
class ExpenseForm(forms.Form):
CHOICES = (
(11, 'Credit Card'),
(12, 'Student Loans'),
(13, 'Taxes'),
(21, 'Books'),
(22, 'Games'),
(31, 'Groceries'),
(32, 'Restaurants'),
)
date = forms.DateField()
category = forms.ChoiceField(choices=CHOICES)
它能渲染出:
使用分组下拉框
还可以使用如下方式生成 <optgourp> 标签：
class ExpenseForm(forms.Form):
CHOICES = (
('Debt', (
(11, 'Credit Card'),
(12, 'Student Loans'),
(13, 'Taxes'),
)),
('Entertainment', (
(21, 'Books'),
(22, 'Games'),
)),
('Everyday', (
(31, 'Groceries'),
(32, 'Restaurants'),
)),
)
date = forms.DateField()
category = forms.ChoiceField(choices=CHOICES)
能够渲染为：
分组模型下拉框
如果使用的是 ModelChoiceField ，那抱歉，Django本身没有提供解决方案。
在 https://code.djangoproject.com/ticket/27331 中提供了一个很好的解决方案。
首先为需要分类的类型创建模型，在另一个模型中用外键关联它：
from django.db import models
class Category(models.Model):
name = models.CharField(max_length=30)
parent = models.ForeignKey('Category', on_delete=models.CASCADE, null=True)
def __str__(self):
return self.name
class Expense(models.Model):
amount = models.DecimalField(max_digits=10, decimal_places=2)
date = models.DateField()
category = models.ForeignKey(Category, on_delete=models.CASCADE)
def __str__(self):
return self.amount
其次，创建一个新的表单 Field 类型：
from functools import partial
from itertools import groupby
from operator import attrgetter
from django.forms.models import ModelChoiceIterator, ModelChoiceField
class GroupedModelChoiceIterator(ModelChoiceIterator):
def __init__(self, field, groupby):
self.groupby = groupby
super().__init__(field)
def __iter__(self):
if self.field.empty_label is not None:
yield ("", self.field.empty_label)
queryset = self.queryset
# Can't use iterator() when queryset uses prefetch_related()
if not queryset._prefetch_related_lookups:
queryset = queryset.iterator()
for group, objs in groupby(queryset, self.groupby):
yield (group, [self.choice(obj) for obj in objs])
class GroupedModelChoiceField(ModelChoiceField):
def __init__(self, *args, choices_groupby, **kwargs):
if isinstance(choices_groupby, str):
choices_groupby = attrgetter(choices_groupby)
elif not callable(choices_groupby):
raise TypeError('choices_groupby must either be a str or a callable accepting a single argument')
self.iterator = partial(GroupedModelChoiceIterator, groupby=choices_groupby)
super().__init__(*args, **kwargs)
最后，在表单中可以如下进行使用：
from django import forms
from .fields import GroupedModelChoiceField
from .models import Category, Expense
class ExpenseForm(forms.ModelForm):
category = GroupedModelChoiceField(
queryset=Category.objects.exclude(parent=None),
choices_groupby='parent'
)
class Meta:
model = Expense
fields = ('amount', 'date', 'category')
