Issue with PyAMF, Django, and Python's "property" feature

So far, I've had great success using PyAMF to communicate between my Flex front-end and my Django back-end. However, I believe I've encountered a bug. The following example (emphasis on the word "example") demonstrates the (potential) bug:

My Flex app contains the following VO:

package myproject.model.vo
{
    [Bindable]
    [RemoteClass(alias="myproject.models.Book")]

    public class BookVO
    {
        public var id:int;
        public var title:String;
        public var numberOfOddPages:int;
    }
}

My Django app contains the following model:

class Book(models.Models):
    title = models.CharField(max_length=20)

    def _get_number_of_odd_pages(self):
        #some code that calculates odd pages
       return odd_page_total

    numberOfOddPages = property(_get_number_of_odd_pages)

When I attempt to retrieve the book objects to display in a DataGrid, the books display in the grid as expected. However, "numberOfOddPages" is always set to 0. I have even attempted to explicitly set this attribute with a default value (i.e., "numberOfOddPages=100") to see if my "_get_number_of_odd_pages()" method had an error in it. Unfortunately, it yields the same result: the value in the VO remains at 0.

Does anyone have any insight into what I may be doing wrong?

Solution

I just received the following response from PyAMF's lead developer. It's definitely a bug:

This is a bug in the way the Django adapter handles non models.fields.* properties.

If I do:

import pyamf

class Book(object):    
def _get_number_of_odd_pages(self):
  return 52

numberOfOddPages = property(_get_number_of_odd_pages)

pyamf.register_class(Book, 'Book')

encoded = pyamf.encode(Book()).getvalue() 
print pyamf.decode(encoded).next().numberOfOddPages

Then i get the correct values of 52.

I have created a ticket for this and will look into getting a patch a little later.

Cheers,

Nick

UPDATE: Nick has fixed this bug and it will be released in PyAMF 0.4.1 (which should be released this weekend).