Django ModelMultipleChoiceField对象没有属性to_field_name

问题描述

我正在尝试为ModelForm创建一个自定义字段.我从ModelMultipleChoiceField进行了扩展，然后覆盖了render和render_options，但是，在尝试导入表单时，我总是收到此异常:

I'm trying to create a custom field for a ModelForm. I'm extending from ModelMultipleChoiceField and then overriding render and render_options, however, I keep getting this exception when just trying to import my form:

AttributeError: 'ModelMultipleChoiceField' object has no attribute 'to_field_name'

我不确定我缺少什么.我什至尝试在我的新类中添加to_field_name属性，但这无济于事.这是我的代码:

I'm not sure what I'm missing. I've tried even adding a to_field_name attribute to my new class, but that doesn't help. Here is my code:

class MultiSelect(ModelMultipleChoiceField):
def __init__(self, queryset, cache_choices=False, required=True,
             widget=None, label=None, initial=None, help_text=None, *args, **kwargs):
    super(MultiSelect, self).__init__(queryset, cache_choices, required, widget,
            label, initial, help_text, *args, **kwargs)

def render_options(self, name, choices, selected_choices):
    output = []
    i = 0
    for option_value, option_label in chain(self.choices, choices):
        checked_html = (option_value in selected_choices) and u' checked="checked"' or ''
        class_html = (i % 2 == 0) and u'even' or u'odd'
        output.append('<li class="{0}"><input type="checkbox" name="{1}" value="{2}"{3}/>{4}</li>'
                .format(class_html, name, escape(option_value), checked_html, escape(option_label)))
        i += 1

def render(self, name, value, attrs=None, choices=()):
    if value is None: value = []
    final_attrs = self.build_attrs(attrs, name=name)
    output = [u'<ul class="multiSelect">']
    options = self.render_options(name, choices, value)
    if options:
        output.append(options)
    output.append('</ul>')
    return mark_safe(u'\n'.join(output))


class RoleForm(ModelForm):
    class Meta:
        model = Role
        exclude = ('user_id',)
        widgets = {
            'permissions': MultiSelect(queryset=Permission.objects.all())
        }

每当我简单地执行from myapp.forms import RoleForm时，都会收到上述错误.

Whenever I simply do an from myapp.forms import RoleForm, I get the error above.

我应该在我的课堂上添加一些我想念的东西吗?

Should I be adding something to my class that I'm missing?

推荐答案

您似乎对字段和小部件感到困惑.您从ModelMultipleChoiceField继承，该名称(顾名思义)是一个字段，而不是窗口小部件.但是render和render_options是窗口小部件(而不是字段)上的方法.您已经在widgets词典中使用了您的课程.

You seem to have got confused between fields and widgets. You inherit from ModelMultipleChoiceField, which (as the name implies) is a field, not a widget. But render and render_options are methods on widgets, not fields. And you've used your class in the widgets dictionary.

我怀疑您确实是要创建小部件.您应该从小部件类(可能是forms.CheckboxSelectMultiple)继承.

I suspect you do mean to create a widget. You should inherit from a widget class, probably forms.CheckboxSelectMultiple.

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