iOS8扩展后台NSURLSession沙箱报错

Question

我正在尝试使用后台 NSURLSession 从照片应用中的共享扩展上传文件。因为后台 NSURLSession 仅支持使用 uploadTaskWithRequest:WithFile: API 的上传任务，所以我首先获取从扩展中检索到的图像 URL 的 URL，将图像内容写入共享容器，然后上传新文件。似乎 NSURLSession 有权限问题，我收到此错误：

“无法为文件 file:///private/var/mobile/Containers/Shared/AppGroup/...发出沙盒扩展...”

我知道有一些类似的帖子，但没有一个是从扩展加载 url，也没有显示将临时文件写入何处。

代码如下：

- (void)fetchImageURLInExtensionContext:(NSExtensionContext*) context onComplete:(void (^)()) completion
{
    NSExtensionItem *item = self.extensionContext.inputItems[0];
    NSItemProvider *provider = item.attachments[0];
    if ([provider hasItemConformingToTypeIdentifier:@"public.jpeg"]) {
        [provider loadItemForTypeIdentifier:@"public.jpeg" options:nil completionHandler:^(id<NSSecureCoding> item, NSError *error) {
            NSObject *obj = item;
            if ([obj isKindOfClass:[NSURL class]]) {
                self.imageURL = obj;
                completion();
            }
        }];
    }
}

- (void)postImage
{
    // copy file to shared container
    NSURL *containerURL = [[NSFileManager defaultManager] containerURLForSecurityApplicationGroupIdentifier:@"group.com.mytestgroup"];
    NSString *writeToPath = [[containerURL path] stringByAppendingPathComponent:@"temp.jpg"];
    BOOL success = [[NSData dataWithContentsOfURL:self.imageURL] writeToFile:writeToPath atomically:YES];

    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"https://api.imgur.com/3/image"]];
    NSString *boundary = @"multipartboundary";
    [request addValue:[NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary] forHTTPHeaderField:@"Content-Type"];
    request.HTTPMethod = @"POST";
    [request setValue:@"Client-ID my_imgur_client_id" forHTTPHeaderField:@"Authorization"];

    NSURLSessionConfiguration *config = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:@"blah"];
    config.sharedContainerIdentifier = @"group.com.mytestgroup";

    NSURLSession *session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];
    NSURLSessionTask *uploadTask = [session uploadTaskWithRequest:request fromFile:[NSURL fileURLWithPath:writeToPath]];
    [uploadTask resume];
}

Answer 1

解决方法：将文件从收件箱移动到临时目录并从那里上传。