objective-c - 委托(delegate)问题

Question

我不明白为什么我无法设置委托(delegate)。我正在使用 UINavigationController 在两个 View 之间切换。这是我的代码

SecondViewProtocol.h

#import <Foundation/Foundation.h>

@protocol SecondViewProtocol <NSObject>
    @required
    -(void)textFieldDidChange:(NSString *)data;
@end

SecondView.h

#import <UIKit/UIKit.h>
#import "SecondViewProtocol.h"
@interface SecondView : UIViewController

@property (nonatomic, retain) id<SecondViewProtocol>delegate;
@end

第二 View .m

@synthesize delegate = _delegate;
.......

-(IBAction)textFieldReturn:(id)sender
{
    [[self delegate] textFieldDidChange:[self.textField text]];
}

.......

我已在 FirstView.h 中导入 SecondViewProtocol.h

FirstView.m

....
SecondView *secondView = [[SecondView alloc]init];
secondView.delegate = self;
....

这里我得到了Assigning to id from incompromed type FirtView。

这里出了什么问题？

Answer 1

首先，委托(delegate)属性应声明为assign，而不是retain。你永远不应该保留委托(delegate)。其次，FirstView 应符合 SecondViewProtocol，如下所示。

@interface FirstView: UIViewController <SecondViewProtocol>