试图创建一个协议，越来越无法找到协议声明

Question

我创建了一些像UIAlertView。 我试图接近创造它做了什么苹果，所以我创建一个类名为MyAlertView并创建了一个协议称为MyAlertViewDelegate，我在类中调用委托属性，但我得到

找不到协议声明

下面是完整的代码：

#import <UIKit/UIKit.h> 
#import "AlertView.h" 


@interface MyAlertView : NSObject 
- (id)initWithTitle:(NSString *)title message:(NSString *)message delegate:(id /*<UIAlertViewDelegate>*/)delegate cancelButtonTitle:(NSString *)cancelButtonTitle otherButtonTitles:(NSString *)otherButtonTitles, ... NS_REQUIRES_NIL_TERMINATION; 

@property(nonatomic,assign) id<MyAlertViewDelegate> delegate; // weak reference 
@property(nonatomic,copy) NSString *title; 
@property(nonatomic,copy) NSString *message; // secondary explanation text 
@property(nonatomic,strong) UIWindow *myWindow; 
@property(nonatomic,strong) AlertView *alertView; 

// adds a button with the title. returns the index (0 based) of where it was added. buttons are displayed in the order added except for the 
// cancel button which will be positioned based on HI requirements. buttons cannot be customized. 
- (NSInteger)addButtonWithTitle:(NSString *)title; // returns index of button. 0 based. 
- (NSString *)buttonTitleAtIndex:(NSInteger)buttonIndex; 
@property(nonatomic,readonly) NSInteger numberOfButtons; 
@property(nonatomic) NSInteger cancelButtonIndex;  // if the delegate does not implement -alertViewCancel:, we pretend this button was clicked on. default is -1 

@property(nonatomic,readonly) NSInteger firstOtherButtonIndex; // -1 if no otherButtonTitles or initWithTitle:... not used 
@property(nonatomic,readonly,getter=isVisible) BOOL visible; 

// shows popup alert animated. 
- (void)show; 

// hides alert sheet or popup. use this method when you need to explicitly dismiss the alert. 
// it does not need to be called if the user presses on a button 
- (void)dismissWithClickedButtonIndex:(NSInteger)buttonIndex animated:(BOOL)animated; 

// Alert view style - defaults to UIAlertViewStyleDefault 
@property(nonatomic,assign) UIAlertViewStyle alertViewStyle NS_AVAILABLE_IOS(5_0); 

/* Retrieve a text field at an index - raises NSRangeException when textFieldIndex is out-of-bounds. 
The field at index 0 will be the first text field (the single field or the login field), the field at index 1 will be the password field. */ 
- (UITextField *)textFieldAtIndex:(NSInteger)textFieldIndex NS_AVAILABLE_IOS(5_0); 

@end 

@protocol MyAlertViewDelegate <NSObject> 
@optional 

// Called when a button is clicked. The view will be automatically dismissed after this call returns 
- (void)alertView:(MyAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex; 

// Called when we cancel a view (eg. the user clicks the Home button). This is not called when the user clicks the cancel button. 
// If not defined in the delegate, we simulate a click in the cancel button 
- (void)alertViewCancel:(MyAlertView *)alertView; 

//- (void)willPresentAlertView:(NSString *)alertView; // before animation and showing view 
- (void)didPresentAlertView:(MyAlertView *)alertView; // after animation 

- (void)alertView:(MyAlertView *)alertView willDismissWithButtonIndex:(NSInteger)buttonIndex; // before animation and hiding view 
- (void)alertView:(MyAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex; // after animation 

// Called after edits in any of the default fields added by the style 
- (BOOL)alertViewShouldEnableFirstOtherButton:(MyAlertView *)alertView; 

@end 

在这一行：@property(nonatomic,assign) id<MyAlertViewDelegate> delegate; // weak reference我得到的错误

Cannot find protocol declaration for 'MyAlertViewDelegate'; did you mean 'UIAlertViewDelegate'? 

它如何知道关于UIAlertViewDelegate的一切？为什么它不承认我自己的协议？

Answer 1

您必须添加@protocol MyAlertViewDelegate您@interface声明像上面：

@protocol MyAlertViewDelegate; 

@interface MyAlertView : NSObject