GitLocker: The Coding Marketplace

Description:

isolated worker

A singleton isolated worker for all platforms. On most platforms, it uses Flutter's Isolate, except on the web, since Isolate is not available, it uses Worker instead.
Features #

💙 Easy to use*
👬 Identical syntax to the compute function provided by Flutter*
🚫 Not a one-off worker
🌐 Available on web**

*except on web
**by using JsIsolatedWorker
Usage #
Basic example #
int doSomeHeavyCalculation(int count) {
// ...
}
void main() {
// if using compute function:
// compute(doSomeHeavyCalculation, 1000);
IsolatedWorker().run(doSomeHeavyCalculation, 1000);
}
copied to clipboard
If we want to do some heavy work that does not need any arguments and/or return values.
// WRONG
void doSomethingHeavy() {
// ...
}

// CORRECT
void doSomethingHeavy(void _) {
// ...
}

void main() {
IsolatedWorker().run(doSomethingHeavy, null);
}

copied to clipboard
Web example #
We can utilize the JsIsolatedWorker for spawning a web worker. However, it cannot use Dart closures as messages to the worker because of some limitations (I have tried using JSONfn and allowInterop but no luck).
Instead we need to use native JS closures. In order to do this, we can utilize existing JS APIs or by importing external libraries/files.
Let's assume we want to stringify objects using JSON.stringify.
void main() {
JsIsolatedWorker().run(
functionName: ['JSON', 'stringify'],
arguments: {},
// optional argument, in case web worker is not available.
fallback: () {
return '{}';
},
).then(print);
// prints "{}"
}
copied to clipboard
Now let's assume we have external js libraries/files that we want the worker to use.
void main() async {
// import the scripts first
// and check if web worker is available
final bool loaded = await JsIsolatedWorker().importScripts(['myModule1.js']);
// web worker is available
if(loaded) {
print(await JsIsolatedWorker().run(
functionName: 'myFunction1',
arguments: 'Hello from Dart :)',
));
}else{
print('Web worker is not available :(');
}
}
copied to clipboard
Shared Platform Worker #
There might be a case where we need to use both IsolatedWorker and JsIsolatedWorker. There are many ways to go about it. We can use conditional import, dependency injections, or WorkerDelegator.
WorkerDelegator #
For example, we have a foo Dart method that returns a list of numbers from 1 to count.
List<int> foo(int count) {
List<int> result = <int>[];
for(int i = 1; i <= count; i++) {
result.add(i);
}
return result;
}
copied to clipboard
And a JS file foo.js containing a foo JS method that does the same thing.
function foo(count) {
let result = [];
for(let i = 1; i <= count; i++) {
result.push(i);
}
return result;
}
copied to clipboard
To call these methods using WorkerDelegator, we need to create a DefaultDelegate, JsDelegate, and WorkerDelegate first. Then register the WorkerDelegate to our WorkerDelegator.
Future<void> main() async {
const DefaultDelegate<int, List<int>> fooDelegate =
DefaultDelegate(callback: foo);

const JsDelegate fooJsDelegate = JsDelegate(callback: 'foo');

const WorkerDelegate<int, List<int>> workerDelegate =
WorkerDelegate(
key: 'foo',
defaultDelegate: fooDelegate,
jsDelegate: fooJsDelegate,
);

WorkerDelegator().addDelegate(workerDelegate);

// Don't forget to call importScripts for our "foo" js method.
await WorkerDelegator().importScripts(const <String>['foo.js']);
}
copied to clipboard
After registering our WorkerDelegate, we just need to call it using its key "foo".
...
print(await WorkerDelegator().run('foo', 9));
...
copied to clipboard
The key can be anything except null.
enum DelegateKeys { foo, bar }
const WorkerDelegate<int, List<int>> workerDelegate =
WorkerDelegate(
key: DelegateKeys.foo,
defaultDelegate: fooDelegate,
jsDelegate: fooJsDelegate,
);
copied to clipboard
Notes: WorkerDelegator() is a singleton. If we need to create a new instance, we can create one using
WorkerDelegator.asNewInstance(
delegates: /* pass our WorkerDelegates here. OPTIONAL. */
);
copied to clipboard
Web Worker Setup #
In order for JsIsolatedWorker to run properly on Flutter web, there needs to be a single worker.js file in the web folder. You can download it here and put it in your web folder like below
...
web /
index.html
worker.js
...
copied to clipboard
Examples #

Fetch - an example of how to get response from a URL using IsolatedWorker and JsIsolatedWorker