Xcode4 - Declaring an object in header file

For example one, I declare an object inside the interface brace {} like:

@interface testViewController : UIViewController {
    IBOutlet UILabel * myLabel;
}
@property (retain, nonatomic) UILabel *myLabel;

@end

and example two, I declare an object outside the inferface brace {} like:

@interface testViewController : UIViewController {
}
@property (retain, nonatomic) IBOutlet UILabel *myLabel;

@end

I run the c开发者_如何学Pythonode and the result is the same, so I want to ask what is the different for decalare an object inside or outside the interface brace {}?

Thanks

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The modern Objective-C runtimes (64-bit Mac OS X and iOS) will generate the backing store for your declared properties when you @synthesize them. So you don't need to declare them within the braces.

If you are declaring an iVar that is not a property and will only be used by the class, then they need to be declared. It's a good idea to mark these @private e.g

@interface MyClass : NSObject {
@private
    NSString *privateString;
}
@property (nonatomic, copy) NSString *publicString; // be sure to @synthesize this
@end

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In the second example you only declare a property. Xcode will declare object automatically.