How to camera on in iphone sdk

.h File:

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController<UIImagePickerControllerDelegate, UINavigationControllerDelegate>
{
    IBOutlet UIButton *btn;
    IBOutlet UIImageView *imageView;
}
@property(nonatomic, retain) IBOutlet UIImageView *imageView;


@end






.m File:


- (void)picturePicker:(UIImagePickerControllerSourceType)theSource {
   
  
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
   
    picker.delegate = self;
    picker.sourceType = theSource;
    picker.allowsEditing = YES;
    
    [self presentModalViewController:picker animated:YES];
   
    [picker release];
}

- (IBAction) takePicture:(id)sender {
   
    if([UIImagePickerController isCameraDeviceAvailable: UIImagePickerControllerCameraDeviceRear] || [UIImagePickerController isCameraDeviceAvailable: UIImagePickerControllerCameraDeviceFront])
    {
         UIImagePickerControllerSourceType source = UIImagePickerControllerSourceTypeCamera;
   
         if ([UIImagePickerController isSourceTypeAvailable:source]) {
       
         [self picturePicker:source];
       
        }
    }
   
    else
    {
        UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"Message" message:@"There is no Camera on your device" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil];
        [alert show];
        [alert release];
    }
}

-(void)imagePickerController:(UIImagePickerController *)picker
      didFinishPickingImage : (UIImage *)image
                 editingInfo:(NSDictionary *)editingInfo
{
    imageView.image = image;
   
    [picker dismissModalViewControllerAnimated:YES];
 }