Get current user in Model Serializer

I found the answer looking through the DRF source code.

class ActivitySerializer(serializers.ModelSerializer):
    
    # Create a custom method field
    current_user = serializers.SerializerMethodField('_user')

    # Use this method for the custom field
    def _user(self, obj):
        request = self.context.get('request', None)
        if request:
            return request.user

    class Meta:
        model = Activity
        # Add our custom method to the fields of the serializer
        fields = ('id','current_user')

The key is the fact that methods defined inside a ModelSerializer have access to their own context, which always includes the request (which contains a user when one is authenticated). Since my permissions are for only authenticated users, there should always be something here.

This can also be done in other built-in djangorestframework serializers.

As Braden Holt pointed out, if your user is still empty (ie _user is returning None), it may be because the serializer was not initialized with the request as part of the context. To fix this, simply add the request context when initializing the serializer:

serializer = ActivitySerializer(
    data=request.data,
    context={
        'request': request
    }
)