django自定义Field实现一个字段存储以逗号分隔的字符串

实现了在一个字段存储以逗号分隔的字符串，返回一个相应的列表

代码如下:

from django import forms
from django.db import models
from django.utils.text import capfirst
from django.core import exceptions

class MultiSelectFormField(forms.MultipleChoiceField):
widget = forms.CheckboxSelectMultiple

def __init__(self, *args, **kwargs):
self.max_choices = kwargs.pop('max_choices', 0)
super(MultiSelectFormField, self).__init__(*args, **kwargs)

def clean(self, value):
if not value and self.required:
raise forms.ValidationError(self.error_messages['required'])
# if value and self.max_choices and len(value) > self.max_choices:
# raise forms.ValidationError('You must select a maximum of %s choice%s.'
# % (apnumber(self.max_choices), pluralize(self.max_choices)))
return value

class MultiSelectField(models.Field):
__metaclass__ = models.SubfieldBase

def get_internal_type(self):
return "CharField"

def get_choices_default(self):
return self.get_choices(include_blank=False)

def _get_FIELD_display(self, field):
value = getattr(self, field.attname)
choicedict = dict(field.choices)

def formfield(self, **kwargs):
# don't call super, as that overrides default widget if it has choices
defaults = {'required': not self.blank, 'label': capfirst(self.verbose_name),
'help_text': self.help_text, 'choices': self.choices}
if self.has_default():
defaults['initial'] = self.get_default()
defaults.update(kwargs)
return MultiSelectFormField(**defaults)

def get_prep_value(self, value):
return value

def get_db_prep_value(self, value, connection=None, prepared=False):
if isinstance(value, basestring):
return value
elif isinstance(value, list):
return ",".join(value)

def to_python(self, value):
if value is not None:
return value if isinstance(value, list) else value.split(',')
return ''

def contribute_to_class(self, cls, name):
super(MultiSelectField, self).contribute_to_class(cls, name)
if self.choices:
func = lambda self, fieldname = name, choicedict = dict(self.choices): ",".join([choicedict.get(value, value) for value in getattr(self, fieldname)])
setattr(cls, 'get_%s_display' % self.name, func)

def validate(self, value, model_instance):
arr_choices = self.get_choices_selected(self.get_choices_default())
for opt_select in value:
if (int(opt_select) not in arr_choices): # the int() here is for comparing with integer choices
raise exceptions.ValidationError(self.error_messages['invalid_choice'] % value)
return

def get_choices_selected(self, arr_choices=''):
if not arr_choices:
return False
list = []
for choice_selected in arr_choices:
list.append(choice_selected[0])
return list

def value_to_string(self, obj):
value = self._get_val_from_obj(obj)
return self.get_db_prep_value(value)