Class

NSURLSessionTask

The NSURLSessionTask class is the base class for tasks in a URL session. Tasks are always part of a session; you create a task by calling one of the task creation methods on an NSURLSession object. The method you call determines the type of task.

Overview

URL sessions provide three types of tasks: data tasks, upload tasks, and download tasks. These tasks are instances of the NSURLSessionDataTask, NSURLSessionUploadTask, NSURLSessionDownloadTask, NSURLSessionStreamTask subclasses of NSURLSessionTask, respectively.

  • Data tasks request a resource, returning the server’s response as one or more NSData objects in memory. They are supported in default, ephemeral, and shared sessions, but are not supported in background sessions.

  • Upload tasks are like data tasks, except that they make it easier to provide a request body so you can upload data before retrieving the server’s response. Additionally, upload tasks are supported in background sessions.

  • Download tasks download a resource directly to a file on disk. Download tasks are supported in any type of session.

  • Stream tasks establish a TCP/IP connection from a host name and port or a net service object.

After you create a task, you start it by calling its resume method. The session then maintains a strong reference to the task until the request finishes or fails; you do not need to maintain a reference to the task unless it is useful to do so for your app’s internal bookkeeping purposes.

Symbols

Controlling the Task State

- cancel

Cancels the task.

- resume

Resumes the task, if it is suspended.

- suspend

Temporarily suspends a task.

state

The current state of the task—active, suspended, in the process of being canceled, or completed.

priority

The relative priority at which you’d like a host to handle the task, specified as a floating point value between 0.0 (lowest priority) and 1.0 (highest priority).

Obtaining Task Progress

countOfBytesExpectedToReceive

The number of bytes that the task expects to receive in the response body.

countOfBytesReceived

The number of bytes that the task has received from the server in the response body.

countOfBytesExpectedToSend

The number of bytes that the task expects to send in the request body.

countOfBytesSent

The number of bytes that the task has sent to the server in the request body.

Obtaining General Task Information

currentRequest

The URL request object currently being handled by the task.

originalRequest

The original request object passed when the task was created.

response

The server’s response to the currently active request.

taskDescription

An app-provided description of the current task.

taskIdentifier

An identifier uniquely identifies the task within a given session.

error

An error object that indicates why the task failed.

Constants

NSURLSessionTaskState

Constants for determining the current state of a task.

URL Session Task Priority

Constants for providing task priority hints to a host, used with the priority property.

Relationships

Inherits From

Conforms To