Objective-C中使用委托模式实现网络请求

该示例代码演示了在Objective-C中使用委托模式实现简单的网络请求，以异步方式获取数据并更新用户界面。通过NSURLConnection发送HTTP请求，利用委托模式处理异步回调。

#import <Foundation/Foundation.h>

// 创建委托协议
@protocol NetworkDelegate <NSObject>
- (void)didReceiveData:(NSData *)data;
- (void)didFailWithError:(NSError *)error;
@end

@interface NetworkManager : NSObject <NSURLConnectionDelegate, NSURLConnectionDataDelegate>
@property (nonatomic, weak) id<NetworkDelegate> delegate;

- (void)requestDataFromURL:(NSURL *)url;
@end

@implementation NetworkManager

- (void)requestDataFromURL:(NSURL *)url {
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    [connection start];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    // 数据接收成功，通过委托通知
    [self.delegate didReceiveData:data];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    // 请求失败，通过委托通知
    [self.delegate didFailWithError:error];
}

@end

// 在使用的地方设置委托并处理数据
@interface ViewController () <NetworkDelegate>
@property (nonatomic, strong) NetworkManager *networkManager;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.networkManager = [[NetworkManager alloc] init];
    self.networkManager.delegate = self;
    NSURL *url = [NSURL URLWithString:@"https://api.example.com/data"];
    [self.networkManager requestDataFromURL:url];
}

- (void)didReceiveData:(NSData *)data {
    // 处理接收到的数据，更新UI等操作
    NSLog(@"接收到数据：%@", [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
}

- (void)didFailWithError:(NSError *)error {
    // 处理请求失败，显示错误信息等操作
    NSLog(@"请求失败：%@", error.localizedDescription);
}

@end

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