event_object 1.0.1

This package will help you to create and manage events, by creating event objects that fires with payload.

Events

This package will help you to create and manage events, by creating event objects that fires with payload.

Usage

import 'package:event_object/event_object.dart';

Examples

Example 1

This example shows how to use Event.historyLimit to control history mode.

void main() {
  // by setting [historyLimit] to 0 we enable history mode with unlimited payloads
  final event = Event<String>(name: 'event', historyLimit: 0);

  print('add listener 1');
  event.addListener((payload) {
    print('event listener 1: $payload');
  });

  print('fire payload 1');
  event.fire('payload 1');

  print('fire payload 2');
  event.fire('payload 2');

  print('add listener 2');
  event.addListener((payload) {
    print('event listener 2: $payload');
  });

  print('fire payload 3');
  event.fire('payload 3');

  print('add listener 3');
  event.addListener((payload) {
    print('event listener 3: $payload');
  });
}

results:

add listener 1
fire payload 1
event listener 1: payload 1

fire payload 2
event listener 1: payload 2

add listener 2
event listener 2: payload 1
event listener 2: payload 2

fire payload 3
event listener 1: payload 3
event listener 2: payload 3

add listener 3
event listener 3: payload 1
event listener 3: payload 2
event listener 3: payload 3

Example 2

This example shows how to use Event.convertTo method This method is useful when you want to convert payload of a type to another type

void main() {
  final event1 = Event<int>(name: 'event1');
  final event2 = Event<String>(name: 'event2');

  // add listener for the first event
  event1.addListener((payload) {
    print('event1 listener: $payload, type: ${payload.runtimeType}');
  });

  // add listener for the seconds event
  event2.addListener((payload) {
    print('event2 listener: $payload, type: ${payload.runtimeType}');
  });

  // convert payload from String to int
  event1.convertTo<String>(event2, (payload) => payload.toString());

  event1.fire(5); // fire event1 with payload 5
}

results:

event1 listener: 5, type: int
event1 listener: 5, type: String

Example 3

This example shows how to use Event.notify and Event.onNext methods to create notification events and how to delay notifications

void main() async {
  final event = Event(); // the payload type is dynamic

  // because payload type is dynamic then we can use [Event.notify] method
  event.notify(Duration(seconds: 5)); // will fire after 5 seconds

  print('waiting for notification...');

  // !Note: the fired payload value is null
  await event.onNext(); // waiting for the fired payload

  print('notification received');
}

results:

waiting for notification...
notification received // after 5 seconds

Example 4

This example shows how to use Events to create reactive variable

void main() async {
  // set [historyLimit] to 1 to just save 1 copy (the latest value)
  final name = Event<String>(name: 'name', historyLimit: 1);

  // set silent to true to prevent calling listeners with the initial value
  name.fire('John', silent: true);

  // add listener to be called when the value changes
  name.addListener((payload) {
    print('name changed to $payload');
  });

  name.fire('Doe'); // set value to 'Doe'

  // set value to 'John Doe' after 5 seconds
  name.fire('John Doe', delay: Duration(seconds: 5));
  
  // ignore 1 fire call
  final newName = await name.onNext(1); // ignores 'Doe' and wait for 'John Doe'

  print('new name is $newName');
}

results:

name changed to Doe
name changed to John Doe // after 5 seconds
new name is John Doe