尽管我完全同意chrisdpratt的说法,但不幸的是,我不得不另外做到这一点。这里有一种方法,我发现这样做在http://djangosnippets.org/snippets/1200/:
from django.db import models
from django import forms
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_db_prep_value(self, value):
if isinstance(value, basestring):
return value
elif isinstance(value, list):
return ",".join(value)
def to_python(self, value):
if isinstance(value, list):
return value
return value.split(",")
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)
你是绝对正确的,我的意思是多对多(这就是为什么还提到了连接表),但最后写为外键。但问题是有一个有500万行的连接表是更好还是应该将它另存为另一列中的ID数组?如果我使用另一列,那么最好的方法是什么。谢谢! – 2011-06-06 16:35:06
连接表将被编入索引,所以我认为行数并不重要。一般来说,遵循最佳实践总是最佳实践,并且ManyToManyField的行为与在Django中的行为相同,因为软件开发人员几乎普遍认为连接表是处理多对多关系的最佳方式。 – 2011-06-06 22:03:14