iOS 开发：使用代理模式编写 Objective-C 代码示例

以下是一个简单的代理实现的OC代码示例：

@protocol MyDelegate

• (void)didFinishTask;
• (void)didFailTaskWithError:(NSError *)error; @end

@interface MyObject : NSObject @property (nonatomic, weak) id delegate;

• (void)startTask; @end

@implementation MyObject

• (void)startTask { // 执行任务

  // 任务完成后，调用代理方法 if ([self.delegate respondsToSelector:@selector(didFinishTask)]) { [self.delegate didFinishTask]; } else { NSLog(@"Delegate did not respond to didFinishTask"); }

  // 任务失败时，调用代理方法 NSError *error = [NSError errorWithDomain:@"com.example.error" code:0 userInfo:nil]; if ([self.delegate respondsToSelector:@selector(didFailTaskWithError:)]) { [self.delegate didFailTaskWithError:error]; } else { NSLog(@"Delegate did not respond to didFailTaskWithError:"); } }

@end

@interface ViewController () @property (nonatomic, strong) MyObject *myObject; @end

@implementation ViewController

• (void)viewDidLoad { [super viewDidLoad];

  self.myObject = [[MyObject alloc] init]; self.myObject.delegate = self;

  [self.myObject startTask]; }

#pragma mark - MyDelegate

• (void)didFinishTask { NSLog(@"Task finished successfully"); }

• (void)didFailTaskWithError:(NSError *)error { NSLog(@"Task failed with error: %@", error); }

@end

在上面的示例中，MyObject是一个包含代理的类，当执行任务完成或失败时，调用代理方法。ViewController是一个使用MyObject类的视图控制器，它遵循MyDelegate协议，并实现了代理方法。当任务完成或失败时，ViewController会接收到相应的回调，并执行相应的操作。