Django CheckboxSelectMultiple 覆盖 ModelForm 中的“选择”

Question

我希望能够在我的 django 表单中提取不同的信息：

这是我的表格：

<form action="" method="post">{% csrf_token %}
{{ form.as_p }}
<input type="submit" value="Submit" />
</form>

class InstanceForm(ModelForm):
    class Meta:
        model = models.BaseAsset
        widgets = {
            'labels': LabelIconCheckboxSelectMultiple()
        }

型号：

class AssetClass(models.Model):
    default_labels = models.ManyToManyField(Label, null=True, blank=True)
    pass

M2M 参考字段

class Label(models.Model):
    explanation = models.CharField(null=True, max_length=63)
    svgpreview  = models.CharField(null=True, max_length=31)
    def __unicode__(self):
        return unicode(self.explanation)
    pass

现在{{ form.as_p }}生成的HTML代码如下：

<li><label for="id_labels_0"><input type="checkbox" name="labels" value="1" id="id_labels_0" /> Consult owner before using</label></li>
<li><label for="id_labels_1"><input type="checkbox" name="labels" value="2" id="id_labels_1" /> This item is broken</label></li>

这意味着它显然使用了模型“标签”的__unicode__ 渲染。如何在 Select 小部件中更改该行为，以便它使用不同的函数来填充它的选择？我正在尝试以合理便携的方式在复选框旁边打印'<img src="{{label.svgpreview}}" alt="{{label.explanation}}"...>'？

Answer 1

这里的 Django 文档对此进行了解释： https://docs.djangoproject.com/en/1.9/ref/forms/fields/#django.forms.ModelChoiceField.to_field_name

您可以在此处看到 ModelChoiceField 类调用字段上的方法： https://github.com/django/django/blob/1155843a41af589a856efe8e671a796866430049/django/forms/models.py#L1174

如果您没有显式覆盖 choices，那么您的代码可能如下所示：

class RectificationAssetMultiField(forms.ModelMultipleChoiceField):
    def label_from_instance(self, obj):
        return '[{0.pk}] {0.label} ({0.location})'.format(obj)


class RectificationForm(forms.ModelForm):
    items = RectificationAssetMultiField(
        required=False,
        queryset=InspectionItem.objects.all(),
        widget=forms.CheckboxSelectMultiple,
        label="Non-compliant Assets"
    )

    class Meta:
        model = Rectification
        fields = ('ref', 'items', 'status')

请注意，这仅在您不直接设置 choices 时才有效（请参阅上述 URL 中的 _get_choices）。

如果您想要覆盖选择（以获得比查询集更有效的结果，或者更好地表示为 ValuesList），那么您将拥有如下内容：

class RectificationAssetMultiField(forms.ModelMultipleChoiceField):
    def label_from_instance(self, obj):
        return '[{0.pk}] {0.label} ({0.location})'.format(obj)


class RectificationForm(forms.ModelForm):
    items = RectificationAssetMultiField(
        required=False,
        queryset=InspectionItem.objects.none(),
        widget=forms.CheckboxSelectMultiple,
        label="Non-compliant Assets"
    )

    def __init__(self, *args, **kwargs):
        super(RectificationForm, self).__init__(*args, **kwargs)
        self.fields['items'].choices = (InspectionItem.objects
            .active()
            .noncompliant()
            .filter(property_id=self.instance.property_id)
            .values_list('pk', 'label') # pass a key value pair
        )

    class Meta:
        model = Rectification
        fields = ('ref', 'items', 'status')

Answer 2

您不必执行“令人毛骨悚然”的实例级覆盖即可充分利用 documented django.forms.models.ModelChoiceField.label_from_instance() 方法。

以原帖中的 AssetClass 和 Label 对象为基础：

class AssetSvgMultiField(forms.ModelMultipleChoiceField):
    """
    Custom ModelMultipleChoiceField that labels instances with their svgpreview.
    """
    def label_from_instance(self, obj):
        return obj.svgpreview


class InstanceForm(forms.ModelForm):
    default_labels = AssetSvgMultiField(queryset=Label.objects.all())

    class Meta:
        model = models.AssetClass
        widgets = {
            'default_labels': forms.CheckboxSelectMultiple()
        }

Answer 3

阅读django.forms.models.ModelChoiceField给出提示：

# this method will be used to create object labels by the QuerySetIterator.
# Override it to customize the label.
def label_from_instance(self, obj):
    """
    This method is used to convert objects into strings; it's used to
    generate the labels for the choices presented by this object. Subclasses
    can override this method to customize the display of the choices.
    """
    return smart_unicode(obj)

好的，但是如何在 ModelForm 的每个实例中覆盖它 - 这在整个 django.forms 的几个地方都会被覆盖

考虑以下代码：

class InstanceForm(ModelForm):
    class Meta:
        model = models.BaseAsset
        widgets = {
            'labels': forms.CheckboxSelectMultiple()
        }


    def __init__(self, *args, **kwargs):
        def new_label_from_instance(self, obj):
            return obj.svgpreview

        super(InstanceForm, self).__init__(*args, **kwargs)
        funcType = type(self.fields['labels'].label_from_instance)
        self.fields['labels'].label_from_instance = funcType(new_label_from_instance, self.fields['labels'], forms.models.ModelMultipleChoiceField)

这有点令人毛骨悚然 - 基本上，这是一个更奇怪的实现： Override a method at instance level

请阅读引用线程中的 cmets 以了解为什么这通常是一个坏主意..

Answer 4

您将覆盖forms.widgets.CheckboxSelectMultiple 类：

这是 CheckboxSelectMultiple 类及其渲染函数：

class CheckboxSelectMultiple(SelectMultiple):
    def render(self, name, value, attrs=None, choices=()):
        if value is None: value = []
        has_id = attrs and 'id' in attrs
        final_attrs = self.build_attrs(attrs, name=name)
        output = [u'<ul>']
        # Normalize to strings
        str_values = set([force_unicode(v) for v in value])
        for i, (option_value, option_label) in enumerate(chain(self.choices, choices)):
            # If an ID attribute was given, add a numeric index as a suffix,
            # so that the checkboxes don't all have the same ID attribute.
            if has_id:
                final_attrs = dict(final_attrs, id='%s_%s' % (attrs['id'], i))
                label_for = u' for="%s"' % final_attrs['id']
            else:
                label_for = ''

            cb = CheckboxInput(final_attrs, check_test=lambda value: value in str_values)
            option_value = force_unicode(option_value)
            rendered_cb = cb.render(name, option_value)
            option_label = conditional_escape(force_unicode(option_label))
            output.append(u'<li><label%s>%s %s</label></li>' % (label_for, rendered_cb, option_label))
        output.append(u'</ul>')
        return mark_safe(u'\n'.join(output))

那么你会怎么做：

class MyCheckboxSelectMultiple(CheckboxSelectMultiple):
    def render(self, name, value, attrs=None, choices=()):
        #put your code to have custom checkbox control with icon
        #...
        output.append(u'<li><label%s>%s %s</label></li>' % (label_for, rendered_cb, option_label)) # especially you will be working on this line
        #...

那么你使用widgets=CheckboxSelectMultiple()的地方会变成widgets=MyCheckboxSelectMultiple()

Answer 5

如果您不喜欢该渲染，请不要使用 {{ form.as_p }}。

改为循环遍历表单：

<form action="/contact/" method="post">
    {% for field in form %}
        <div class="fieldWrapper">
            {{ field.errors }}
            {{ field.label_tag }}: {{ field }}
        </div>
    {% endfor %}
    <p><input type="submit" value="Send message" /></p>
</form>

然后您就可以随意使用任何您想要的 HTML。

发件人：https://docs.djangoproject.com/en/dev/topics/forms/#looping-over-the-form-s-fields