description

# spawn<T> method Null safety

Future<Isolate> spawn <T>(

1. void entryPoint(
   1. T message
   ),
2. T message,
3. {bool paused: false,
4. bool errorsAreFatal: true,
5. SendPort? onExit,
6. SendPort? onError,
7. @Since("2.3") String? debugName}

)

Creates and spawns an isolate that shares the same code as the current isolate.

The argument `entryPoint` specifies the initial function to call in the spawned isolate. The entry-point function is invoked in the new isolate with `message` as the only argument.

The function must be a top-level function or a static method that can be called with a single argument, that is, a compile-time constant function value which accepts at least one positional parameter and has at most one required positional parameter. The function may accept any number of optional parameters, as long as it can be called with just a single argument. The function must not be the value of a function expression or an instance method tear-off.

Usually the initial `message` contains a SendPort so that the spawner and spawnee can communicate with each other.

If the `paused` parameter is set to `true`, the isolate will start up in a paused state, just before calling the `entryPoint` function with the `message`, as if by an initial call of `isolate.pause(isolate.pauseCapability)`. To resume the isolate, call `isolate.resume(isolate.pauseCapability)`.

If the `errorsAreFatal`, `onExit` and/or `onError` parameters are provided, the isolate will act as if, respectively, setErrorsFatal, addOnExitListener and addErrorListener were called with the corresponding parameter and was processed before the isolate starts running.

If `debugName` is provided, the spawned Isolate will be identifiable by this name in debuggers and logging.

If `errorsAreFatal` is omitted, the platform may choose a default behavior or inherit the current isolate's behavior.

You can also call the setErrorsFatal, addOnExitListener and addErrorListener methods on the returned isolate, but unless the isolate was started as `paused`, it may already have terminated before those methods can complete.

Returns a future which will complete with an Isolate instance if the spawning succeeded. It will complete with an error otherwise.

## Implementation

    external static Future<Isolate> spawn<T>(
        void entryPoint(T message), T message,
        {bool paused = false,
        bool errorsAreFatal = true,
        SendPort? onExit,
        SendPort? onError,
        @Since("2.3") String? debugName});