StreamController
- Flutter course
- Intermediate
- Lesson 28/99
- 4 min
Create your own Stream with StreamController.
StreamController
StreamController lets you create your own Stream. You send values to the stream with sink.add and listen via the stream property.
final controller = StreamController<int>();
controller.sink.add(1);
controller.stream.listen(print);This is the way to produce data programmatically.
sink and stream
controller.sink.add(value) sends a new value to the stream. controller.stream is the Stream used to listen to these values.
controller.sink.add('hello');
controller.stream.listen((value) {
print(value);
});Values from the stream are delivered to listeners.
Practice Send data with StreamController
In the VeriYoneticisi class, hold a StreamController<String>. The veriGonder method should call controller.sink.add(deger). The stream getter should return controller.stream. In main, create the manager, send 'merhaba' and call print('yönetici hazır').
Starter code
import 'dart:async';
class VeriYoneticisi {
// kontrolcü tanımla
// veriGonder metodu ekle
// stream getter ekle
}
void main() {
final yonetici = VeriYoneticisi();
yonetici.veriGonder('merhaba');
print('yönetici hazır');
}Sample solution
import 'dart:async';
class VeriYoneticisi {
final controller = StreamController<String>();
void veriGonder(String deger) {
controller.sink.add(deger);
}
Stream<String> get stream => controller.stream;
}
void main() {
final yonetici = VeriYoneticisi();
yonetici.veriGonder('merhaba');
print('yönetici hazır');
}Expected output
yönetici hazır
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What is StreamController used for?
- You create your own Stream Correct answer
- A widget is drawn
- A stream listener is added
- It produces a Future
Explanation: With StreamController you create your own Stream; you send values with sink.add and listen via stream.
2 Send a value with sink.add
controller.sink.____('merhaba');controller.sink.add('merhaba');Explanation: controller.sink.add sends a new value to the stream; listeners receive this value.
3 StreamController parts
| Term | Meaning |
|---|---|
StreamController |
Class creating your own Stream |
sink |
Channel to add data to stream |
stream |
Listenable stream |
add |
Method to send value via sink |