[__NSCFDictionary objectAtIndex:]: unrecognized selector sent to instance
Solution 1:
The problem is that feed is not a NSArray, but a NSDictionary.
Looking at the JSON, you likely want to access this array: [feed objectForKey:@"entry"]
Solution 2:
The top level object in your feed is a JSON object, not a JSON array. So the deserialisation gives you an NSDictionary, not an NSArray.