如何利用RestKit和ObjectiveC采集搜狐音频

```objc
#import
#import
@interface AudioDownloader : NSObject
+ (void)downloadAudioWithURLString:(NSString *)urlString completionHandler:(void (^)(NSURL *filePath, NSError *error))completionHandler;
@end
@implementation AudioDownloader
+ (void)downloadAudioWithURLString:(NSString *)urlString completionHandler:(void (^)(NSURL *filePath, NSError *error))completionHandler {
// 1. 创建一个AFHTTPSessionManager对象
AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
// 2. 设置代理，用于获取proxy
[manager setProxy:[[[AFProxy alloc] init] autorelease]];
// 3. 使用get_proxy方法获取proxy
[manager.proxy getProxy:^(NSArray *proxies) {
// 4. 从proxies数组中选择一个proxy
NSURLProxy *proxy = [proxies firstObject];
// 5. 设置代理服务器
manager.proxy = proxy;
// 6. 创建一个RestKit的RequestDescriptor对象
RKRequestDescriptor *requestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:[self audioMapping] objectClass:[NSData class] rootKeyPath:nil];
// 7. 使用RestKit发送请求
[manager.router sendRequest:[RKRequest requestWithURL:urlString] descriptor:requestDescriptor completionHandler:^(RKResponse *response, NSError *error) {
// 8. 检查是否有错误
if (error) {
completionHandler(nil, error);
return;
}
// 9. 获取音频数据
NSData *audioData = response.parsedBody;
// 10. 保存音频数据到文件
NSURL *filePath = [self saveAudioData:audioData withFileName:[urlString lastPathComponent]];
// 11. 调用completionHandler回调，传入文件路径和错误信息
completionHandler(filePath, nil);
}];
}];
}
// 12. 保存音频数据到文件
+ (NSURL *)saveAudioData:(NSData *)audioData withFileName:(NSString *)fileName {
// ...
}
// 13. 返回音频的映射
+ (RKObjectMapping *)audioMapping {
// ...
}
@end
```