Understanding ios and objective-c @property

Question

What is the difference between:

@interface PhotoAppViewController : UIViewController <UIImagePickerControllerDelegate, UINavigationControllerDelegate>
{
    UIImageView * imageView;
    UIButton * choosePhotoBtn;
    UIButton * takePhotoBtn;
}

@property (nonatomic, retain) IBOutlet UIImageView * imageView;
@property (nonatomic, retain) IBOutlet UIButton * choosePhotoBtn;
@property (nonatomic, retain) IBOutlet UIButton * takePhotoBtn;

And this:

@interface PhotoAppViewController : UIViewController <UIImagePickerControllerDelegate, UINavigationControllerDelegate>

@property (nonatomic, retain) IBOutlet UIImageView * imageView;
@property (nonatomic, retain) IBOutlet UIButton * choosePhotoBtn;
@property (nonatomic, retain) IBOutlet UIButton * takePhotoBtn;

What do the curly braces mean after the delegation?

Answer 1

From http://rypress.com/tutorials/objective-c/properties.html:

An object’s properties let other objects inspect or change its state. But, in a well-designed object-oriented program, it’s not possible to directly access the internal state of an object. Instead, accessor methods (getters and setters) are used as an abstraction for interacting with the object’s underlying data.

Stackoverflow Answer