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uploadTask(with:fromFile:completionHandler:)

Creates a task that performs an HTTP request for uploading the specified file, then calls a handler upon completion.

Declaration

func uploadTask(with request: URLRequest, fromFile fileURL: URL, completionHandler: @escaping  @Sendable (Data?, URLResponse?, (any Error)?) -> Void) -> URLSessionUploadTask

Parameters

  • request:

    A URL request object that provides the URL, cache policy, request type, and so on. The body stream and body data in this request object are ignored.

  • fileURL:

    The URL of the file to upload.

  • completionHandler:

    The completion handler to call when the load request is complete. This handler is executed on the delegate queue.

    If you pass nil, only the session delegate methods are called when the task completes, making this method equivalent to the Uploadtask(with:fromfile:) method.

    This completion handler takes the following parameters:

    data

    The data returned by the server.

    response

    An object that provides response metadata, such as HTTP headers and status code. If you are making an HTTP or HTTPS request, the returned object is actually an Httpurlresponse object.

    error

    An error object that indicates why the request failed, or nil if the request was successful.

Return Value

The new session upload task.

Discussion

An HTTP upload request is any request that contains a request body, such as a POST or PUT request. Upload tasks require you to create a request object so that you can provide metadata for the upload, like HTTP request headers.

Unlike uploadTask(with:fromFile:), this method returns the response body after it has been received in full, and does not require you to write a custom delegate to obtain the response body.

By using a completion handler, the task bypasses calls to delegate methods for response and data delivery, and instead provides any resulting data, response, or error inside the completion handler. Delegate methods for handling authentication challenges, however, are still called.

Typically you usually pass a nil completion handler only when creating tasks in sessions whose delegates include a urlSession(_:dataTask:didReceive:) method. However, if you do not need the response data, use key-value observing to watch for changes to the task’s status to determine when it completes.

After you create the task, you must start it by calling its resume() method.

If the request completes successfully, the data parameter of the completion handler block contains the resource data, and the error parameter is nil. If the request fails, the data parameter is nil, and the error parameter contains information about the failure. If a response from the server is received, regardless of whether the request completes successfully or fails, the response parameter contains that information.

See Also

Adding upload tasks to a session