Django：如何在文本输入字段中显示值列表？

Question

I have defined a Model with a ManyToManyField, and I want the field to show the values joined by spaces, for example:

<input type="text" name="foo" value="val1 val2 val3"/>

I have defined the form to use CharField to represent the multiple values:

class MyForm(ModelForm):
    foo = CharField(label='Foo')
    class Meta:
        model = MyModel

Instead of showing the values separated by spaces, the value shows this instead:

[u'val1', u'val2', u'val3']

How can I override this behavior?

Answer 1

You have a basic misunderstanding, which is that fields themselves aren't responsible for how they're rendered. That's what widgets do.

Answer 2

Ok, I finally figured it out:

class MultiValueTextWidget(TextInput):
    def _get_value(self, value):
        return " ".join(value)

    def _format_value(self, value):
        if self.is_localized:
            return formats.localize_input(self._get_value(value))
        return self._get_value(value)

I had tried this earlier (before I posted the original question), but I think there was something wrong with my field declaration. It works when I instantiate the field with the widget like this:

markets = CharField(widget=MultiValueTextWidget(), label='Ticker symbols')

For some reason I had trouble with this:

class Meta:
    widgets = {
        'markets': MultiValueTextWidget()
        }