I'm using Rest Kit 0.20.3 and Xcode 5 to create an application. I've completed the GET request and got my 2 objects from the server. Now I've created an additional View with two text fields to enter playerName and playerAge. 
I've tried the following code to post a new player to the server but its not working:

AddPlayerViewController.h

```
#import <RestKit/RestKit.h>
#import "Player.h"

@interface AddPlayerViewController : UIViewController

@property (nonatomic, strong) Player *addedPlayer;

@property (weak, nonatomic) IBOutlet UITextField *playerNameTxt;
@property (weak, nonatomic) IBOutlet UITextField *playerAgeTxt;

- (IBAction)save:(id)sender;
@end

```

AddPlayerViewController.m

```
@implementation AddPlayerViewController

- (IBAction)save:(id)sender {

    [self postObject];
}

-(void)postObject{

    [[RKObjectManager sharedManager] postObject:addedPlayer path:@"/players.json" parameters:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
        addedPlayer.playerName = playerNameTxt.text;
        NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc]init];
        [numberFormatter setNumberStyle:NSNumberFormatterNoStyle];
        addedPlayer.playerAge = [numberFormatter numberFromString:[NSString stringWithFormat:@"%@",playerAgeTxt.text]];
    } failure:^(RKObjectRequestOperation *operation, NSError *error) {
    }];
}
@end

```

I'm getting the following errror:

```
Expected status code in (200), got 422, AFNetworkingOperationFailingURLResponseErrorKey=<NSHTTPURLResponse: 0xaf67e60> { URL: http://localhost:3000/players.json}

```

AppDelegate.m

```
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    RKLogConfigureByName("RestKit", RKLogLevelWarning);
    RKLogConfigureByName("RestKit/ObjectMapping", RKLogLevelTrace);
    RKLogConfigureByName("RestKit/Network", RKLogLevelTrace);

    RKObjectManager *objectManager = [RKObjectManager managerWithBaseURL:[NSURL URLWithString:@"http://192.168.1.3:3010"]];

    RKObjectMapping *playerMapping = [RKObjectMapping mappingForClass:[Player class]];

    [playerMapping addAttributeMappingsFromDictionary:@{@"id": @"playerID",
                                                        @"name": @"playerName",
                                                        @"age" : @"playerAge",
                                                        @"created_at": @"createdAt",
                                                        @"updated_at": @"updatedAt"}];

    RKResponseDescriptor *responseDesc = [RKResponseDescriptor responseDescriptorWithMapping:playerMapping method:RKRequestMethodAny pathPattern:@"/players.json" keyPath:nil statusCodes:[NSIndexSet indexSetWithIndex:200]];

    [objectManager addResponseDescriptor:responseDesc];

    RKRequestDescriptor *requestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:[playerMapping inverseMapping] objectClass:[Player class] rootKeyPath:@"/players.json" method:RKRequestMethodPOST];

    [objectManager addRequestDescriptor:requestDescriptor];
    return YES;
}

```

Player.h

```
@interface Player : NSObject

@property (nonatomic,strong) NSNumber *playerID;
@property (nonatomic,strong) NSString *playerName;
@property (nonatomic,strong) NSNumber *playerAge;
@property (nonatomic,strong) NSDate *createdAt;
@property (nonatomic,strong) NSDate *updatedAt;

@end

```

On the Server Side I get this:

```
Started POST "/players.json" for 192.168.1.3 at 2013-11-01 20:01:34 +0530
Processing by PlayersController#create as JSON
  Parameters: {"/players.json"=>{"age"=>"40", "name"=>"sachin"}}
Completed 400 Bad Request in 0ms

ActionController::ParameterMissing (param not found: player):
  app/controllers/players_controller.rb:73:in `player_params'
  app/controllers/players_controller.rb:28:in `create'

```