NSURLConnection sendAsynchronousRequestをリトライ機能付きでリクエストする

今回も線形反復のサンプルです。

NSURLConnectionを何度かリトライ込みで記述してみます。

@interface DownloadUtility : NSObject
+ (void)downloadAndRetryWithURL:(NSURL *)url retryCount:(int)retryCount completion:(void(^)(NSURLResponse *response, NSData *data))completion failue:(void(^)())failure;
@end
@implementation DownloadUtility
+ (void)downloadAndRetryWithURL:(NSURL *)url retryCount:(int)retryCount completion:(void(^)(NSURLResponse *response, NSData *data))completion failue:(void(^)())failure
{
    completion = [completion copy];
    failure = [failure copy];

    NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:5];
    [NSURLConnection sendAsynchronousRequest:request
                                       queue:[NSOperationQueue mainQueue]
                           completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
     {
         if(error)
         {
             if(retryCount > 0)
             {
                 NSLog(@"retry");
                 [DownloadUtility downloadAndRetryWithURL:url
                                               retryCount:retryCount - 1
                                               completion:completion
                                                   failue:failure];
             }
             else
             {
                 if(failure)
                     failure();
             }
         }
         else
         {
             if(completion)
                 completion(response, data);
         }
     }];
}
@end


    //呼び出し側
    [DownloadUtility downloadAndRetryWithURL:[NSURL URLWithString:@"http://www.google.co.jp"]
                                  retryCount:5
                                  completion:^(NSURLResponse *response, NSData *data)
    {
        NSLog(@"complete!");
    } failue:^{
        NSLog(@"failure...");
    }];

呼び出し側が非常にシンプルになります。

簡単なフローチャートです。
ただこのコードはフローチャートとの乖離が激しいです
https://cacoo.com/diagrams/wveKhJQz9S00oIMG