Step 1: Create the controller, set the delegate, and conform to the protocol

//Swift
class ImageUploadViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
    
    let imagePickerController = UIImagePickerController()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        imagePickerController.delegate = self
    }
}

//Objective-C
@interface ImageUploadViewController : UIViewController <UIImagePickerControllerDelegate,UINavigationControllerDelegate> {

    UIImagePickerController *imagePickerController;

}

@end

@implementation ImageUploadViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    imagePickerController.delegate = self;

}

@end

note: We actually will not implement anything defined in UINavigationControllerDelegate, but UIImagePickerController inherits from UINavigationController and changes the behavior of UINavigationController. Therefore, we still need to say our view controller conforms to UINavigationControllerDelegate.

Step 2: Whenever you need to show UIImagePickerController:

//Swift
self.imagePickerController.sourceType = .Camera // options: .Camera , .PhotoLibrary , .SavedPhotosAlbum
self.presentViewController(self.imagePickerController, animated: true, completion: nil)

//Objective-C
imagePickerController.sourceType = UIImagePickerControllerSourceTypeCamera; // options: UIImagePickerControllerSourceTypeCamera, UIImagePickerControllerSourceTypePhotoLibrary, UIImagePickerControllerSourceTypeSavedPhotosAlbum
[self presentViewController:imagePickerController animated:YES completion:nil];

Step 3: Implement the delegate methods:

//Swift
func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
    if let pickedImage = info[UIImagePickerControllerOriginalImage] as? UIImage {
        // Your have pickedImage now, do your logic here
    }
    self.dismissViewControllerAnimated(true, completion: nil)
}

func imagePickerControllerDidCancel(picker: UIImagePickerController) {
    self.dismissViewControllerAnimated(true, completion: nil)
}

//Objective-C
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

   UIImage *pickedImage = info[UIImagePickerControllerOriginalImage];

    if (pickedImage) {
    
        //You have pickedImage now, do your logic here
    
    }

    [self dismissViewControllerAnimated:YES completion:nil];

}

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {

    [self dismissViewControllerAnimated:YES completion:nil];

}