ios - 代表iOS

Question

我正在尝试了解为什么无法从协议(protocol)中读取类型。我想这是因为@interface 在协议(protocol)之下，但如果有人能帮我找出问题并向我解释为什么那会很棒。

#import <UIKit/UIKit.h>

@protocol ARCHCounterWidgetDelegate <NSObject>

    - (UIColor *) counterWidget: (ARCHCounterWidget *) counterWidget;

@end

@interface ARCHCounterWidget : UIView

    @property (weak, nonatomic) id<ARCHCounterWidgetDelegate> delegate;

@end

Answer 1

您必须 forward declare类或协议(protocol):

// tell the compiler, that this class exists and is declared later:
@class ARCHCounterWidget;

// use it in this protocol
@protocol ARCHCounterWidgetDelegate <NSObject>
- (UIColor *) counterWidget: (ARCHCounterWidget *) counterWidget;
@end

// finally declare it
@interface ARCHCounterWidget : UIView
@property (weak, nonatomic) id<ARCHCounterWidgetDelegate> delegate;
@end

或:

// tell the compiler, that this protocol exists and is declared later
@protocol ARCHCounterWidgetDelegate;

// now you can use it in your class interface
@interface ARCHCounterWidget : UIView
@property (weak, nonatomic) id<ARCHCounterWidgetDelegate> delegate;
@end

// and declare it here
@protocol ARCHCounterWidgetDelegate <NSObject>
- (UIColor *) counterWidget: (ARCHCounterWidget *) counterWidget;
@end