Returns an initialized NSURLDownload object that will resume downloading the specified data to the specified file and begins the download.


init(resumeData: Data, delegate: NSURLDownloadDelegate?, path: String)



Specifies the data to resume downloading.


The delegate for the download. This object will receive delegate messages as the download progresses. Delegate messages will be sent on the thread which calls this method. For the download to work correctly the calling thread’s run loop must be operating in the default run loop mode.

The NSURLDownload class maintains a strong reference to this delegate object.


The location for the downloaded data.

Return Value

An initialized NSURLDownload object.


If you want to support pausing and resuming downloads, your app must:

  1. Call deletesFileUponFailure, passing false. If you want to support resuming downloads in the event of a lost connection, you should do this immediately after you initialize the download object.

  2. If your app needs to pause the transfer for any reason, call cancel(). Because your app previously called deletesFileUponFailure with false, the in-progress download is not deleted.

  3. After your app pauses the transfer or after a transfer error occurs, call resumeData to obtain the data needed to resume the transfer later.

  4. If the transfer failed because of a connectivity error, use the SCNetworkReachability API to determine an appropriate time to try again. For details, read SCNetworkReachability.

    If your app explicitly paused the download, wait until it is appropriate to continue the transfer (such as when the user clicks or taps a resume button).

  5. Call init(resumeData:delegate:path:) and pass the resume data blob that it previously obtained in step 3.

See Also

Resuming partial downloads

class func canResumeDownloadDecoded(withEncodingMIMEType: String) -> Bool

Returns whether a URL download object can resume a download that was decoded with the specified MIME type.

var resumeData: Data?

Returns the resume data for a download that is not yet complete.

var deletesFileUponFailure: Bool

Returns whether the receiver deletes partially downloaded files when a download stops prematurely.