Question

The following code is not returning private lists:

NSURL* url=[NSURL URLWithString:@"http://api.twitter.com/1/noppefoxwolf/lists.json"];
NSDictionary* params=[NSDictionary dictionaryWithObjectsAndKeys:nil];
TWRequest* timeline=[[TWRequest alloc] initWithURL:url parameters:params requestMethod:TWRequestMethodGET];
timeline.account=_account;
[timeline performRequestWithHandler:^(NSData* responseData,
                                      NSHTTPURLResponse* urlResponse,NSError* error) {
    NSError* jsonError=nil;
    id data=[NSJSONSerialization JSONObjectWithData:responseData
                                            options:0 error:&jsonError];
    if (error!=nil) {
        [self showAlert:@"" text:@"Error1"];
    } else if (jsonError!=nil) {
        [self showAlert:@"" text:@"Error2"];
    } else {
        NSArray * listsArray = [data objectForKey:@"lists"];
        for (int i=0;i<listsArray.count;i++) {
            NSDictionary* listDic=[listsArray objectAtIndex:i];
            NSLog(@"NAME:%@\nMODE:%@",[listDic objectForKey:@"name"],[listDic objectForKey:@"mode"]);
        }
    }
}];

Result

NAME:list1
MODE:public
NAME:list2
MODE:public

↑ Not showing private list.

Answer 1

From the documentation:

Private lists will be included if the authenticated user is the same
as the user whose lists are being returned.

You are passing in no params, so no user_id value is specified (even though the documentation says it is required!). I am guessing noppefoxwolf is not your authenticated user.