Question

I’m developing an iPhone application with latest SDK.

I have this code:

-(void) connectionDidFinishLoading:(NSURLConnection *) connection
{
    NSError* error = nil;
    NSObject* response =
        [NSJSONSerialization JSONObjectWithData:webData
                                        options:NSJSONReadingMutableContainers
                                          error:&error];

    if ([response isKindOfClass:[NSArray class]])
    {
        NSDictionary* resp = [response objectAtIndex:0];

This line, NSDictionary* resp = [response objectAtIndex:0]; doesn’t work. I get this compilation time error: No visible @interface for 'NSObject' declares the selector 'objectAtIndex:'.

I could do something like this:

NSArray* array = [NSArray initWithArray:response]; but I think it will create two objects and it will waste resources.

How do I cast a NSObject to NSArray?

Answer 1

This tutorial explains why I must use id response = instead of NSObject* response =.

If I use id I can send any message to response object.

So, If I have checked if [response isKindOfClass:[NSArray class]] there won’t be any problem if I do [response objectAtIndex:0].

And also, it won’t be any compilation time error.

I’ve added this answer because there will be more people with the same problem.