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https://github.com/stasgora/observetree

Observetree is a library extending the Observable pattern by integrating it in a tree structure with propagating events
https://github.com/stasgora/observetree

events java library listener maven observable pattern tree

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

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# 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 [![Javadocs](https://javadoc.io/badge/dev.sgora/observetree.svg)](https://javadoc.io/doc/dev.sgora/observetree)

Javadoc also available at [sgora.dev/observetree/](https://sgora.dev/observetree/)



For detailed technical description see [Observable class](https://javadoc.io/doc/dev.sgora/observetree/latest/stasgora.observetree/dev/sgora/observetree/Observable.html)



### Installation

#### Maven [![Maven Central](https://img.shields.io/maven-central/v/dev.sgora/observetree.svg)](https://search.maven.org/search?q=g:%22dev.sgora%22%20AND%20a:%22observetree%22)

```xml



  dev.sgora

  observetree

  ${observetree-version}



```

(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](https://github.com/stasgora/observetree/releases) 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```:

```java

class Point extends Observable {

  public int x, y;

}

```

- Internally call ```onValueChanged()```:

```java

private void set(int x, int y) {

  this.x = x;

  this.y = y;

  onValueChanged();

}

```

- Create instance and register a listener:

```java

Point p = new Point();

p.addListener(() -> {...});

```

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

```java

p.set(1, 1);

p.notifyListeners();

```



### Advanced functions

#### Using _Observable_ trees

- Build model structure:

```java

class Model extends Observable {

  public Point point;

  ...

  public Model() {

    addSubObservable(point);

    ...

  }

}

```

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

```java

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:

```java

model.notifyListeners();

```

(For detailed behaviour description see the [documentation](https://javadoc.io/doc/dev.sgora/observetree/latest/stasgora.observetree/dev/sgora/observetree/Observable.html))

#### Specifying listener priority

```java

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

```

#### Creating _Settables_ out of external objects

- Declare:

```java

SettableProperty size = new SettableProperty<>(1);

```

- Get notified when the value is set:

```java

size.set(2);

```

#### Using _Settable Observables_ with persistent listeners

- Declare:

```java

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

```

- Register static listener:

```java

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

```

- After replacing the object the listeners will remain attached:

```java

point.set(new Point());

```



### Author

Stanisław Góra



### License

[MIT License](http://www.opensource.org/licenses/mit-license.php)