description

# spawnUri method Null safety

Future<Isolate> spawnUri (

1. Uri uri,
2. List<String> args,
3. dynamic message,
4. {bool paused: false,
5. SendPort? onExit,
6. SendPort? onError,
7. bool errorsAreFatal: true,
8. bool? checked,
9. Map<String, String>? environment,
10. @Deprecated('The packages/ dir is not supported in Dart 2') Uri? packageRoot,
11. Uri? packageConfig,
12. bool automaticPackageResolution: false,
13. @Since("2.3") String? debugName}

)

Creates and spawns an isolate that runs the code from the library with the specified URI.

The isolate starts executing the top-level `main` function of the library with the given URI.

The target `main` must be callable with zero, one or two arguments. Examples:

- `main()`
- `main(args)`
- `main(args, message)`

When present, the parameter `args` is set to the provided `args` list. When present, the parameter `message` is set to the initial `message`.

If the `paused` parameter is set to `true`, the isolate will start up in a paused state, 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.

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.

If the `checked` parameter is set to `true` or `false`, the new isolate will run code in checked mode (enabling asserts and type checks), respectively in production mode (disabling asserts and type checks), if possible. If the parameter is omitted, the new isolate will inherit the value from the current isolate.

In Dart2 strong mode, the `checked` parameter only controls asserts, but not type checks.

It may not always be possible to honor the `checked` parameter. If the isolate code was pre-compiled, it may not be possible to change the checked mode setting dynamically. In that case, the `checked` parameter is ignored.

WARNING: The `checked` parameter is not implemented on all platforms yet.

If the `packageConfig` parameter is provided, then it is used to find the location of a package resolution configuration file for the spawned isolate.

If the `automaticPackageResolution` parameter is provided, then the location of the package sources in the spawned isolate is automatically determined.

The `environment` is a mapping from strings to strings which the spawned isolate uses when looking up String.fromEnvironment values. The system may add its own entries to environment as well. If `environment` is omitted, the spawned isolate has the same environment declarations as the spawning isolate.

WARNING: The `environment` parameter is not implemented on all platforms yet.

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

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

## Implementation

    external static Future<Isolate> spawnUri(
        Uri uri,
        List<String> args,
        var message,
        {bool paused = false,
        SendPort? onExit,
        SendPort? onError,
        bool errorsAreFatal = true,
        bool? checked,
        Map<String, String>? environment,
        @Deprecated('The packages/ dir is not supported in Dart 2')
            Uri? packageRoot,
        Uri? packageConfig,
        bool automaticPackageResolution = false,
        @Since("2.3")
            String? debugName});