Python 如何构造具有ModelChoiceField的Django表单？

我正在尝试为我的表单编写一个测试，该表单使用自定义ModelChoiceField：

from django.forms import ModelChoiceField
class CycleModelChoiceField(ModelChoiceField):
    def label_from_instance(self, cycle):
        return str(cycle.begin_date)

用户在此字段中选择的任何内容都需要通过重写

clean（）

方法传递到其他两个字段（DateField和radio ChoiceField）。这是我需要测试的复杂逻辑

以下是我在测试中尝试过的：

self.client.login(username='user', password='1234')
response = self.client.get(reverse('my_form'), follow=True)
cyc = list(CycleDate.objects.all())[0]
form_data = {'type_of_input': '0', 'cycle': cyc,'usage_type': 'E',}
form = EnergyUsageForm(data=form_data, user=response.context['user'])

但是

form.is\u valid（）

返回false，并且

form.errors

显示：

{'cycle': [u'Select a valid choice. That choice is not one of the available choices.']}

我的表单结构一定有问题<代码>“循环”：cyc显然没有按预期工作。我还尝试了

'cycle'：'0'

和

'cycle'：'1'

构造这样一个表单的正确方法是什么

编辑： 我应该解释一下有哪些选择。数据库中只有一个CycleDate，只有一个选项。在shell中运行测试行之后，我键入了

form.fields['cycle'].choices.choice（cyc）

，返回

（1，'2015-05-01'）

。奇怪的是

form.fields['cycle'].queryset

返回

[]

。也许问题与此有关

EDIT2: 这是我的表格，上面有一个复杂的（读作：凌乱、可怕和可耻的）清洁方法：

class EnergyUsageForm(forms.Form):
    # Override init so that we can pass the user as a parameter.
    # Then put the cycle form inside init so that it can access the current user variable
    def __init__(self, *args, **kwargs):
        user = kwargs.pop('user', None)
        super(EnergyUsageForm, self).__init__(*args, **kwargs)

        # Get the last 12 cycle dates for the current user
        td = datetime.date.today
        cycle_dates = CycleDate.objects.filter(cycle_ref=Account.objects.get(holder__user=user).cycle,
                                               begin_date__lte=td).order_by('begin_date')
        self.fields['cycle'] = CycleModelChoiceField(queryset = cycle_dates,
                                                      required = False,
                                                      widget = forms.Select(attrs={"onChange":'changeCalendar()'}),
                                                      label = "Choose a billing cycle")


    type_of_input = forms.ChoiceField(required=False,
                                    widget=forms.Select(attrs={"onChange": "switchInput()"}),
                                    choices=INPUT,
                                    initial='0',
                                    label="Choose a way to display usage", )

    end_date = forms.DateField(widget=forms.TextInput(attrs=
                                {
                                    'class':'datepicker'
                                }), 
                                label="Choose start date",
                                help_text='Choose a beginning date for displaying usage',
                                required=True,
                                initial=datetime.date.today,)

    period = forms.ChoiceField(required=True,
                                widget=forms.RadioSelect, 
                                choices=DISPLAY_PERIOD, 
                                initial='01',
                                label="Choose period to display",)

    usage_type = forms.ChoiceField(required=True,
                                widget=forms.RadioSelect,
                                choices=USAGE_TYPE,
                                initial='E',
                                label="Choose type of usage to display",)

    def clean_end_date(self):
        data = self.cleaned_data['end_date']

        if datetime.date.today() < data:
            raise forms.ValidationError("Don't choose a future date")
        # Always return the cleaned data, whether you have changed it or
        # not.
        return data

    def clean(self):
        cleaned_data = super(EnergyUsageForm, self).clean()
        selection = cleaned_data['type_of_input']
        # Check if the user wants to use cycle_dates instead
        if selection == '0':
            # Set the end_date and period
            cleaned_data['end_date'] = cleaned_data['cycle'].begin_date #MUST BE CHANGED TO END_DATE LATER
            cleaned_data['period'] = cleaned_data['cycle'].duration
        return cleaned_data

EDIT4:

---

除了这些混乱之外，每当我调用

form.is\u valid（）

，我都会得到

KeyError:“cycle”

。可能是由于clean（）方法试图在cycle字段具有无效选择时访问cleaned_数据['cycle']。

正如DanielRoseman所指出的，答案是使用实例的id

因此，使用ModelChoiceField构造表单的正确方法如下：

my_instance = MyModelName.objects.get(whatever instance you need)
form_data = {'my_regular_choice_field': '0', 'my_model_choice_field': my_instance.id}
form = MyFormName(data=form_data)

特别是线路

cyc = list(CycleDate.objects.all())[0]

• 首先，您得到所有CycleDates的迭代器（ok，或多或少ok…）
• 然后你把所有的东西都读到了记忆中（为什么！）
• 最后。。您选择第一个列表元素（当然，如果列表为空，您将得到异常…）

为什么不：

cyc = CycleDate.objects.first()
if cyc:
    # cycle is a ModelChoice - in html it stores primary key!
    form_data = {'type_of_input': '0', 'cycle': cyc.pk, 'usage_type': 'E'}
    form = EnergyUsageForm(data=form_data, user=response.context['user'])

EnergyUsageForm的初始值：

def __init__(self, *args, **kwargs):
    user = kwargs.pop('user', None)
    super(EnergyUsageForm, self).__init__(*args, **kwargs)

    # today is a function!
    td = datetime.date.today()
    account = Account.objects.get(holder__user=user)
    cycle_dates = CycleDate.objects.filter(cycle_ref=account.cycle,
                                           begin_date__lte=td)
                                   .order_by('begin_date')

    self.fields['cycle'] = CycleModelChoiceField(queryset=cycle_dates,
                                                 required=False,
                                                 widget=forms.Select(attrs={"onChange":'changeCalendar()'}),
                                                 label = "Choose a billing cycle")

---

无论是哪种方式，请使用

Cycle.objects.first（）

而不是调用

list

来计算查询集。请显示您的表单定义，包括“复杂”的干净逻辑。另外，关于

'Cycle'：cyc.id

？我看到填充该字段的查询取决于用户。您确定您的Cycle对象与您传入的用户正确相关吗？正如我提到的，您没有将Cycle对象与用户关联，因此查询不会返回任何值。

cyc = CycleDate.objects.first()
if cyc:
    # cycle is a ModelChoice - in html it stores primary key!
    form_data = {'type_of_input': '0', 'cycle': cyc.pk, 'usage_type': 'E'}
    form = EnergyUsageForm(data=form_data, user=response.context['user'])

def __init__(self, *args, **kwargs):
    user = kwargs.pop('user', None)
    super(EnergyUsageForm, self).__init__(*args, **kwargs)

    # today is a function!
    td = datetime.date.today()
    account = Account.objects.get(holder__user=user)
    cycle_dates = CycleDate.objects.filter(cycle_ref=account.cycle,
                                           begin_date__lte=td)
                                   .order_by('begin_date')

    self.fields['cycle'] = CycleModelChoiceField(queryset=cycle_dates,
                                                 required=False,
                                                 widget=forms.Select(attrs={"onChange":'changeCalendar()'}),
                                                 label = "Choose a billing cycle")