URLSessionDownloadTask启动时调用的委托方法是什么？

Question

There are three methods in NSURLSessionDownloadDelegate protocol.

URLSession:downloadTask:didFinishDownloadingToURL:,
URLSession:downloadTask:didResumeAtOffset:expectedTotalBytes:
URLSession:downloadTask:downloadTaskdidWriteData:totalBytesWritten:totalBytesExpectedToWrite:

The didFinishDownloadingToURL is called when the download task complete. But what is the method called when the download task start?

Answer 1

URLSession:downloadTask:downloadTaskdidWriteData:totalBytesWritten:totalBytesExpectedToWrite: this delegate gets called time to time depending on data received, this delegates writes data to file location. furthermore, if anything goes wrong, –URLSession:task:didCompleteWithError: this delegate gives you details about the error.