Exclude a field from tastypie api

Question

I need to exclude a field on the basis of the value of some other field. The relationship between them is as follows.

class Moo: 
   ...

class Too:
        moo = models.ForeignKey(Moo, related_name='moo_too')

        ...

class PooToo:
       moo = models.ForeignKey(Moo) 
       stature = models.PositiveSmallIntegerField(..)
       ...

class PooMooResource(ModelResource):

    moo = ToOneField(StandAloneMooResource, 'moo', full=True)
    class Meta:
        list_allowed_methods = ['get']
        queryset = PooMoo.objects.select_related('moo').all()

class StandAloneMooResource(ModelResource):

    too = ToManyField(TooResource,...)
    class Meta:
            queryset = Moo.objects.all()

Now I want to expose the too field in the API only when stature==0, otherwise not. I can use use_in for this, but the problem is I do not have the value of stature in StandAloneMooResource

Answer 1

Try something like this:

class StandAloneMooResource(ModelResource):

    too = ToManyField(TooResource,...)
    class Meta:
        queryset = Moo.objects.all()

    def dehydrate_too(self, bundle):
        # if this method is run while dehdyrating PooMooResource.moo,
        # related_obj should be the related PooMoo
        if bundle.related_obj and bundle.related_obj.stature != 0:
            return None
        return bundle.data['too']

Unfortunately the 'too' key will still be there, and tastypie will still go through the effort of retrieving the tutorials from the DB.

This might be better:

def foo(bundle):
    if bundle.related_obj and bundle.related_obj.stature != 0:
        return None
    return bundle.obj.tutorials.all()

class StandAloneMooResource(ModelResource):

    too = ToManyField(TooResource, attribute=foo)
    class Meta:
        queryset = Moo.objects.all()

    def dehydrate(self, bundle):
        # to remove the 'tutorials' key
        if 'too' in bundle.data and not bundle.data['too']:
            del bundle.data['too']
        return bundle

If bundle.related_obj isn't working:

def foo(bundle):
    poomoo = None
    try:
        # assumes PooMoo.user a relation to User
        poomoo = PooMoo.objects.filter(moo=bundle.obj, user=bundle.request.user)[0]
    except IndexError:
        pass
    if poomoo and poomoo.stature != 0:
        return None
    return bundle.obj.too.all()