具有自我类型的协议功能

Question

这是代码：

#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
@protocol HomeHeaderCellDelegate <NSObject>
- (void)didTapMoreLessMenuButton:(HomeHeaderCell *)cell;
@end
@interface HomeHeaderCell : UITableViewCell
@property (weak, nonatomic) IBOutlet UIView *secondMenuRowView;
@property (weak, nonatomic) IBOutlet UIButton *moreLessMenuButton;
@property (weak, nonatomic) IBOutlet NSLayoutConstraint *secondMenuRowViewHeightConstraint;
@property (weak, nonatomic) IBOutlet UIButton *askButton;
@property (weak, nonatomic) IBOutlet UIButton *contactButton;
@property (weak, nonatomic) IBOutlet UIButton *benchmarkButton;
@property (weak, nonatomic) IBOutlet UIButton *buySellButton;
@property (weak, nonatomic) IBOutlet UIButton *marketButton;
@property (nonatomic, weak) id <HomeHeaderCellDelegate> delegate;
@property BOOL isFullMenu;
- (void)toggleHeight;
@end
NS_ASSUME_NONNULL_END

此行有错误

- (void)didTapMoreLessMenuButton:(HomeHeaderCell *)cell;

它说：

期望类型

Answer 1

编译器需要知道 HomeHeaderCell在某个地方声明。

实际上，您必须 import 带有@import语句的类，但是在这种情况下，您只需要类型而不是实现详细信息。@class指令是一个正向参考，可确认类型但避免循环参考问题。

在进口行下方添加 @class，顺便说一句，使用现代@import语句。

@import UIKit;
@class HomeHeaderCell;

Answer 2

您可以做

#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
@protocol HomeHeaderCellDelegate;
@interface HomeHeaderCell : UITableViewCell
@property (nonatomic, weak) id <HomeHeaderCellDelegate> delegate;
@end
@protocol HomeHeaderCellDelegate <NSObject>
- (void)didTapMoreLessMenuButton:(HomeHeaderCell *)cell;
@end
NS_ASSUME_NONNULL_END