Summary - Concurrency
- Dart course
- Advanced
- Lesson 12/83
- 5 min
Combine event loop, microtasks and Zone to write a scheduler.
Summary - Concurrency
This group covered Dart's concurrency model: a single-threaded event loop, two queues (event and microtask), the Future scheduler and Zones.
Core principle: microtasks run before events in each turn. Future.value and Future.microtask schedule as microtasks; Future.delayed schedules as an event.
A Zone is an execution-environment abstraction used for async error handling and task interception.
Practice Summary: microtask + event order
Make main async. Add print('başla');. Add await Future.microtask(() => print('micro'));. Add print('bitti');.
Starter code
void main() {
// make async; print 'başla'; microtask prints 'micro'; print 'bitti'
}Sample solution
void main() async {
print('başla');
await Future.microtask(() => print('micro'));
print('bitti');
}Expected output
başla micro bitti
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which adds to the event queue?
- Future.value
- Future.microtask
- scheduleMicrotask
- Future.delayed Correct answer
Explanation: Future.delayed adds a task to the event queue.
2 Match the concepts
| Term | Meaning |
|---|---|
Event loop |
Single thread |
Microtask |
Priority queue |
Future.delayed |
Event queue |
Zone |
Execution environment |
3 Schedule a microtask
____(() => print('m'));scheduleMicrotask(() => print('m'));Explanation: scheduleMicrotask adds to the microtask queue.