stasgora / observetree

Observetree is a library extending the Observable pattern by integrating it in a tree structure with propagating events

Observetree library

Observetree is a library that extends the classic Observable pattern by integrating it in a tree structure. Change events are propagated through the Observable tree. Listeners can be assigned a priority to control the order at which they are called.

Getting started

Documentation

Javadoc also available at sgora.dev/observetree/

For detailed technical description see Observable class

Installation

Maven

<dependency>
  <groupId>dev.sgora</groupId>
  <artifactId>observetree</artifactId>
  <version>${observetree-version}</version>
</dependency>

_{^{(Earlier versions released under io.github.stasgora groupId)}}

SNAPSHOT versions are not synchronized to Central. If you want to use a snapshot version you need to add the https://oss.sonatype.org/content/repositories/snapshots/ repository to your pom.xml.

Manual

See the release page for jar downloads. Follow your IDE instructions for detailed steps on adding external library dependencies to your project.

Basic usage

• Create model class extending Observable:

class Point extends Observable {
  public int x, y;
}

• Internally call onValueChanged():

private void set(int x, int y) {
  this.x = x;
  this.y = y;
  onValueChanged();
}

• Create instance and register a listener:

Point p = new Point();
p.addListener(() -> {...});

• Change model object and allow it to call it's listeners:

p.set(1, 1);
p.notifyListeners();

Advanced functions

Using Observable trees

• Build model structure:

class Model extends Observable {
  public Point point;
  ...
  public Model() {
    addSubObservable(point);
    ...
  }
}

• You can subscribe to changes of objects on different levels:

model.addListener(...); // Changes to model and all it's sub-observables
model.point.addListener(...);

• After changes to potentially many objects notify listeners of all changed objects in tree:

model.notifyListeners();

(For detailed behaviour description see the documentation)

Specifying listener priority

p.addListener(() -> {...}, ListenerPriority.HIGH);

Creating Settables out of external objects

• Declare:

SettableProperty<Integer> size = new SettableProperty<>(1);

• Get notified when the value is set:

size.set(2);

Using Settable Observables with persistent listeners

• Declare:

SettableObservable<Point> point = new SettableObservable<>(new Point());

• Register static listener:

point.addStaticListener(() -> {...});

• After replacing the object the listeners will remain attached:

point.set(new Point());

Author

Stanisław Góra

License

MIT License