Error: 'BoundField' object is not iterable in Python3

[vstoykov]

When I use Python3 an have nested model serializers I see this error:

'BoundField' object is not iterable

I made a little investigation and found that BoundField proxy does not work for some reason.

I run in Python console (both Python2 and Python3) this example code:

 class I():
     def __iter__(self):
         for i in range(5):
             yield i

class BoundI():
    def __init__(self, i):
        self._i = i
    def __getattr__(self, attr):
        return getattr(self._i, attr)

i = I()
bi = BoundI(i)

list(i)  # work
list(bi)  # work only on Python2. In Py3 the error is "object is not iterable"

These example classes use the same logic as Serialzier and BoundField classes in DRF.

[vstoykov]

Hmm now I see that there is a NestedBoundField, but in my case for some reason is created BoundField instead of NestedBoundField.

I will continue with investigation.

[xordoquy]

A bit more context would help, in particular why do you have a BoundField.
You'd usually want to use the serializer's validated_data instead.

[vstoykov]

The problem is caused by this commit 6b08e97

BoundField.as_form_field allways returns BoundField and then when this method is called on NestedBoundField instance then instance of BoundField is returned. When DRF renderds the field with it's template https://github.com/tomchristie/django-rest-framework/blob/master/rest_framework/templates/rest_framework/horizontal/fieldset.html then in the {% for nested_field in field %} the exception is raised.

@tomchristie can you look at this because you implemented as_form_field and probably you have something in mind.

[tomchristie]

Yup sounds like a bug against master as part of resolving some other stuff. I'll have a dig.
If you're able to include the smallest possible set of code that could replicate this that'd be wonderful, but no worries if not.

[vstoykov]

I will try to write something tomorrow.

This affects only browsable API. If you just get JSON responses via AJAX, everything is working normally.

[tomchristie]

Now resolved. Thanks for the report!

[vstoykov]

I think that it is not. Now it raises 'str' object has no attribute 'get'. I will check first if this is related to my code but I think that this is not the reason .

[tomchristie]

Noted. Shame we don't yet have test coverage over this.

[tomchristie]

Okay, looks sane to me now. Worth verifying @vstoykov?

[vstoykov]

It's ok now. I've created a test that will fail if executed before last change. After the last change is Ok. You can look at it and if you are ok with it I can make a pull request.

vstoykov@20e0e68

[tomchristie]

@vstoykov That would probably be a good plan - thanks!