我在一个单独的文件(myProtocol.h)中定义了一个协议.这是它的代码：
#import <Foundation/Foundation.h>
@protocol myProtocol <NSObject>
-(void) loadDataComplete;
@end
firstViewController.h：
#import "myProtocol.h"
@interface firstViewController : UIViewController{
id <myProtocol> delegate;
}
@property (retain) id delegate;
-(void) mymethod;
firstViewController.m
@implementation firstViewController
@synthesize delegate;
- (void)viewDidLoad {
[self mymethod];
}
-(void) mymethod {
//some code here...
[delegate loadDataComplete];
}
我有另一个文件,其中也使用协议：
secondViewController.h：
#import "myProtocol.h"
@interface secondViewController : UIViewController<myProtocol>{
}
secondViewController.m：
-(void) loadDataComplete{
NSLog(@"loadDataComplete called");
}
但我的secondViewController没有调用协议美联储.为什么会这样？任何建议将不胜感激.
解决方法
首先,正如@Abizern建议的那样,尝试重新格式化代码.使用大写字母表示课程.这里说这个解答你的答案.
这是协议.我将它命名为FirstViewControllerDelegate,因为实现该对象的类是FirstViewController的委托.
#import <Foundation/Foundation.h> @protocol MyProtocol <NSObject> - (void)doSomething; @end
这是SecondViewController.
#import <UIKit/UIKit.h>
#import "MyProtocol.h"
@interface SecondViewController : UIViewController <MyProtocol>
@end
@implementation SecondViewController
// other code here...
- (void)doSomething
{
NSLog(@"Hello FirstViewController");
}
@end
这是FirstViewController.
#import <UIKit/UIKit.h>
@interface FirstViewController : UIViewController
// it coud be better to declare these properties within a class extension but for the sake of simplicity you could leave here
// the important thing is to not declare the delegate prop with a strong/retain property but with a weak/assign one,otherwise you can create cycle
@property (nonatomic,strong) SecondViewController* childController;
@property (nonatomic,weak) id<MyProtocol> delegate;
@end
@implementation FirstViewController
// other code here...
- (void)viewDidLoad
{
[super viewDidLoad];
self.childController = [[SecondViewController alloc] init];
self.delegate = self.childController; // here the central point
// be sure your delegate (SecondViewController) responds to doSomething method
if(![self.delegate respondsToSelector:@selector(doSomething)]) {
NSLog(@"delegate cannot respond");
} else {
NSLog(@"delegate can respond");
[self.delegate doSomething];
}
}
@end
为了完整起见,请务必了解委托模式的含义. Apple doc是你的朋友.您可以查看the-basics-of-protocols-and-delegates以获得参数的基本介绍.此外,SO搜索允许您找到关于该主题的大量答案.
希望有所帮助.
