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In an .h file, what is the difference between:
@interface ViewController : UIViewController
@property (strong, nonatomic) UIView* myView;
And
@interface ViewController : UIViewController{
UIView* myView;
}
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An opaque type that represents an instance variable. iOS 4.0+ iPadOS 4.0+ macOS 10.5+ tvOS 9.0+ watchOS 2.0+
Property attributes are special keywords to tell compiler how to generate the getters and setters. Here you specify two property attributes: nonatomic, which tells the compiler not to worry about multithreading, and retain, which tells the compiler to retain the passed-in variable before setting the instance variable.
For a private/protected variable, use iVar; for a public variable, use property. If you want to use the benifit of property attributes for a private variable, like retain, nonatomic etc., declare the property in the implementation file as a private property. For an iVar, you can use @private , @protected and @public .
Therefore, as a fundamental principal of object-oriented programming, instance variables (ivars) are private—they are encapsulated by the class. By contrast, a property is a public value that may or may not correspond to an instance variable.
The first one is the declaration of a property, whereas the second is only a ivar. A property is the automatic declaration of a getter and a setter for an ivar, but if there is not ivar (like in your first example) the property will create the ivar too.
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