python - Django:将 'choices' 从另一个数据库传递到 MultipleChoiceField

Question

我有一个模型，其中有一个应该是多选的字段。我为此创建了一个ModelForm。在此，我查询另一个数据库以获得用户应该能够选择的可能选项。

class CollaborationForm(forms.ModelForm):
    cursor = connections['diseases'].cursor()
    cursor.execute('select some_column from some_table')
    all_cuis = cursor.fetchall()
    cui = forms.MultipleChoiceField(choices=all_cuis, help_text='Relevant CUI, can select more than one')

    class Meta:
        model = Collaboration
        fields = '__all__'

MultipleChoiceField 仅采用元组作为选择参数。碰巧这正是 cursor.fetchall() 返回的结果。唯一的问题是这个元组看起来像这样:

(('value1',), ('value2',),...))

由于元组中没有第二个值，django 会抛出错误:

not enough values to unpack (expected 2, got 1)

元组应该是不可变的，所以我觉得以某种方式再次添加相同的值以使错误消失是非常hacky的。另一方面，将元组放入列表，然后再次放入元组似乎也是错误的。有更好的方法吗？

Answer 1

您需要键值对，例如:

class CollaborationForm(forms.ModelForm):
    cursor = connections['diseases'].cursor()
    cursor.execute('select some_column from some_table')
    all_cuis = cursor.fetchall()
    cui = forms.MultipleChoiceField(
        <b>choices=[(c[0],c[0]) for c in all_cuis]</b>,
        help_text='Relevant CUI, can select more than one'
    )

    class Meta:
        model = Collaboration
        fields = '__all__'

但请注意，在加载 CollaborationForm 类时，您只会运行查询一次。您可能希望将选项的创建移至 __init__ 方法。例如:

class CollaborationForm(forms.ModelForm):
    cui = forms.MultipleChoiceField(
        <b>choices=[]</b>,
        help_text='Relevant CUI, can select more than one'
    )

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        cursor = connections['diseases'].cursor()
        cursor.execute('select some_column from some_table')
        all_cuis = cursor.fetchall()
        <b>self.fields['cui'].choices = [c*2 for c in all_cuis]</b>

    class Meta:
        model = Collaboration
        fields = '__all__'