我们可以在objective-c中创建可空/非空的属性吗？

Question

如果是，那么我们可以在objective-c中创建可空/非空的属性吗？

Answer 1

You can use _Nullable and _Nonnull qualifiers

@property (copy, nullable) NSString *name;
@property (copy, nonnull) NSArray *allItems;

nonnull: Indicates that the pointer should/will never be nil. Pointers annotated with nonnull are imported into Swift as their non-optional base value (ie, NSData).

nullable: Indicates that the pointer can be nil in general practice. Imported into Swift as an optional value (NSURL?).

Answer 2

You can use _Nullable and _Nonnull qualifiers as you see fit. (Put them in the same place as you'd place a const qualifier).