Update CDM mapper to handle transformable core data attributes.

gistfile1.m

- (Class)expectedClassForObject:(NSManagedObject *)object andKey:(id)key
{
    NSDictionary *attributes = [[object entity] attributesByName];
    NSAttributeDescription *attributeDescription = [attributes valueForKey:key];
    NSString *className = [attributeDescription attributeValueClassName];
    if (!className) {
        const char *className = [[object.entity managedObjectClassName] cStringUsingEncoding:NSUTF8StringEncoding];
        const char *propertyName = [key cStringUsingEncoding:NSUTF8StringEncoding];
        
        Class managedObjectClass = objc_getClass(className);
        objc_property_t prop = class_getProperty(managedObjectClass, propertyName);
        
        NSString *attributeString = [NSString stringWithCString:property_getAttributes(prop) encoding:NSUTF8StringEncoding];
        const char *destinationClassName = [[self propertyTypeFromAttributeString:attributeString] cStringUsingEncoding:NSUTF8StringEncoding];
        
        return objc_getClass(destinationClassName);
    } else {
        return NSClassFromString(className);
    }
}

- (NSString *)propertyTypeFromAttributeString:(NSString *)attributeString
{
    NSString *type = [NSString string];
    NSScanner *typeScanner = [NSScanner scannerWithString:attributeString];
    [typeScanner scanUpToCharactersFromSet:[NSCharacterSet characterSetWithCharactersInString:@"@"] intoString:NULL];
    
    if ([typeScanner isAtEnd]) {
        return @"NULL";
    } else {
        [typeScanner scanCharactersFromSet:[NSCharacterSet characterSetWithCharactersInString:@"\"@"] intoString:NULL];
        [typeScanner scanUpToCharactersFromSet:[NSCharacterSet characterSetWithCharactersInString:@"\""] intoString:&type];
        return type;
    }
}