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# start()

Starts the receiver.

```
func start()
```

## Discussion

This method asynchronously spawns the new thread and invokes the receiver’s [`main()`](/documentation/Foundation/Thread/main()) method on the new thread. The [`isExecuting`](/documentation/Foundation/Thread/isExecuting) property returns <doc://com.apple.documentation/documentation/Swift/true> once the thread starts executing, which may occur after the [`start()`](/documentation/Foundation/Thread/start()) method returns.

If you initialized the receiver with a target and selector, the default [`main()`](/documentation/Foundation/Thread/main()) method invokes that selector automatically.

If this thread is the first thread detached in the application, this method posts the [`NSWillBecomeMultiThreaded`](/documentation/Foundation/NSNotification/Name-swift.struct/NSWillBecomeMultiThreaded) with object `nil` to the default notification center.

## See Also

[`init(target:selector:object:)`](/documentation/Foundation/Thread/init(target:selector:object:))

Returns an `NSThread` object initialized with the given arguments.

[`init()`](/documentation/Foundation/Thread/init())

Returns an initialized `NSThread` object.


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