How to get user details using twitter api v1.1 (Twitter error 215)

I have used the twitter api provided by twitter,to get the details but not able to execute it, even tried to pass the authentication data like consumer secret key, consumer key, token but the result is same.
I am able to login and receiving twitter authentication token but not able to get user details. Below code is used by me (I am using MGtwitter engine) :

NSMutableURLRequest *request =[[NSMutableURLRequest alloc]initWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"https://api.twitter.com/1.1/users/show.json?screen_name=%@",username]]];

NSData *returnData = [ NSURLConnection sendSynchronousRequest: request returningResponse: nil error: nil ];

NSString *returnString = [[NSString alloc]initWithData:returnData encoding:NSUTF8StringEncoding];
    NSError *err = nil;

twitterLogin = [NSJSONSerialization JSONObjectWithData:[returnString dataUsingEncoding:NSUTF8StringEncoding] options:NSJSONReadingMutableContainers error:&err];

Error is shown as below:

errors = (
{
    code = 215;
    message = "Bad Authentication data";
} );

First, you need to Authenticate your request (Get permission).

second, see follow these steps:

1.Download FHSTwitterEngine Twitter Library.

2.Add the folder FHSTwitterEngine" to your project and #import "FHSTwitterEngine.h".

3.add SystemConfiguration.framework to your project.

Usage : 1.in the [ViewDidLoad] add the following code.

UIButton *logIn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    logIn.frame = CGRectMake(100, 100, 100, 100);
    [logIn setTitle:@"Login" forState:UIControlStateNormal];
    [logIn addTarget:self action:@selector(showLoginWindow:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:logIn];

[[FHSTwitterEngine sharedEngine]permanentlySetConsumerKey:@"<consumer_key>" andSecret:@"<consumer_secret>"];
    [[FHSTwitterEngine sharedEngine]setDelegate:self];

and don't forget to import the delegate FHSTwitterEngineAccessTokenDelegate.

2. you need to get the permission for your request, with the following method which will present Login window:

- (void)showLoginWindow:(id)sender {
    [[FHSTwitterEngine sharedEngine]showOAuthLoginControllerFromViewController:self withCompletion:^(BOOL success) {
        NSLog(success?@"L0L success":@"O noes!!! Loggen faylur!!!");
    }];
}

when the Login window is presented, enter your Twitter Username and Password to authenticate your request.

3. add the following methods to your code:

-(void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [[FHSTwitterEngine sharedEngine]loadAccessToken];
    NSString *username = [[FHSTwitterEngine sharedEngine]loggedInUsername];// self.engine.loggedInUsername;
    if (username.length > 0) {
        lbl.text = [NSString stringWithFormat:@"Logged in as %@",username];
        [self listResults];


    } else {
        lbl.text = @"You are not logged in.";
    }

}
- (void)storeAccessToken:(NSString *)accessToken {
    [[NSUserDefaults standardUserDefaults]setObject:accessToken forKey:@"SavedAccessHTTPBody"];
}

- (NSString *)loadAccessToken {
    return [[NSUserDefaults standardUserDefaults]objectForKey:@"SavedAccessHTTPBody"];
}

4.Now you are ready to get your request, with the following method(in this method I created a Twitter search for some Hashtag, to get the screen_name for example):

- (void)listResults {

    dispatch_async(GCDBackgroundThread, ^{
        @autoreleasepool {
            [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;

        // the following line contains a FHSTwitterEngine method wich do the search.

            dict = [[FHSTwitterEngine sharedEngine]searchTweetsWithQuery:@"#iOS" count:100 resultType:FHSTwitterEngineResultTypeRecent unil:nil sinceID:nil maxID:nil];
          // NSLog(@"%@",dict);
            NSArray *results = [dict objectForKey:@"statuses"];

          //  NSLog(@"array text = %@",results);
            for (NSDictionary *item in results) {
                NSLog(@"text == %@",[item objectForKey:@"text"]);
                NSLog(@"name == %@",[[item objectForKey:@"user"]objectForKey:@"name"]);
                NSLog(@"screen name == %@",[[item objectForKey:@"user"]objectForKey:@"screen_name"]);
                NSLog(@"pic == %@",[[item objectForKey:@"user"]objectForKey:@"profile_image_url_https"]);
            }

            dispatch_sync(GCDMainThread, ^{
                @autoreleasepool {
                    UIAlertView *av = [[UIAlertView alloc]initWithTitle:@"Complete!" message:@"Your list of followers has been fetched" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
                    [av show];
                    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
                }
            });
        }
    });
}

That's all. I just got the screen_name from a search Query, you can get a timeline for a user using the following methods:

// statuses/user_timeline
- (id)getTimelineForUser:(NSString *)user isID:(BOOL)isID count:(int)count;
- (id)getTimelineForUser:(NSString *)user isID:(BOOL)isID count:(int)count sinceID:(NSString *)sinceID maxID:(NSString *)maxID; 

instead of the search method above.

Note: see the FHSTwitterEngine.h to know what method you need to use. Note: to get the <consumer_key> and the <consumer_secret> you need to to visit this link to register your app in Twitter.