django admin中带有django-taggit字段的FilteredSelectMultiple小部件

Question

I am trying to add Tags to my model instances using django-taggit's package. For this I have added the tags field in my Model as it is defined in django-taggit's definition.

class MyModel(models.Model):
    name = models.CharField(max_length=100)
    tags = TaggableManager()

I want to add this model to django-admin panel and want to use FilteredSelectMultiple widget for adding tags. for this I have created a model form and changed it's field's widget.

class MyModelForm(forms.ModelForm):
    tags = forms.ModelMultipleChoiceField(queryset=Tag.objects.none())
    def __init__(self, *args, **kwargs):
        super(MyModelForm, self).__init__(*args, **kwargs)
        self.fields['tags'].widget = FilteredSelectMultiple('Tags', False)
        self.fields['tags'].queryset = Tag.objects.all()

class Meta:
    model = MyModel
    exclude = []

class MyModelAdmin(admin.ModelAdmin): form = MyModelForm

everything is working fine. Tags are being saved after saving the instace. but the problem is that when I am opening the update page. There are no previously selected tags in 'Chosen Tags' part of the field's widget.It is empty and all the choices are in 'Available tags' option.

I tried to provide initial data also for the change_form of model admin but nothing works for me.

def get_changeform_initial_data(self, request):
    return {'tags': self.object.tags.all()}

self.object is the object which i got by get_object() method of the ModelAdmin class.

Give me a solution.

Answer 1

Seems the problem is that the prepare_value function in ModelMultipleChoiceField looks at the .pk field on the object which gives a value that's incorrect so it does not render (or renders the wrong selection). You should be looking at it's .tag_id field.

This worked for me but would be interested if there is a more correct or elegant way:

class TagMultipleChoiceField(forms.ModelMultipleChoiceField):
    def prepare_value(self, value):
        if hasattr(value, 'tag_id'):
            return value.tag_id
        elif hasattr(value, '__iter__') and not isinstance(value, six.text_type) and not hasattr(value, '_meta'):
            return [self.prepare_value(v) for v in value]
        else:
            return super(TagMultipleChoiceField, self).prepare_value(value)

class AdminCourseForm(forms.ModelForm):
    class Meta:
        model = Course
        exclude = ()

    tags = TagMultipleChoiceField(queryset=MyTag.objects.all())