nonnull、nullable、null_resettable、_Null_unspecified关键字

• iOS 9新增关键字: 用于修饰属性或者方法的参数、方法的返回值

  • nonnull不可为空,等同于_Nonnull和__nonnull

    • e.g.

@property (nonatomic,strong,nonnull) UIView *view;
@property (nonatomic,strong) UIView *_Nonnull view;
@property (nonatomic,strong) UIView *__nonnull view;

• nullable可为空,等同于_Nullable和__nullable

  • e.g.

@property (nonatomic,strong, nullable) UIView *view;
@property (nonatomic,strong) UIView *_Nullable view;
@property (nonatomic,strong) UIView *__nullable view;

• null_resettable setter方法可传空,getter方法不为空

• _Null_unspecified 不确认是否为空