Events

My take on an event system in Java. It was originally developed for Project 16x16 followed by the improved version v2 for Zombiecraft.

V2

Demo | Post

Features

• Reflectionless implementation of events using functional interfaces and generics
• Support for double colon operator :: for example this::onSetup
• Error handeling, for instance parameter check and listener method reference
• trigger(...)
• bind(method) / unbind(method) / unbind()
• bind(method, priority, ignoreCancelled) listener priority and cancel handeling
• bound(method)
• cancel() / setCancelled(cancelled) / isCancelled()
• Event.flush(object) failsafe measure in uncontrolled cases to prevent memory leaks
• Variable<T> implementation to modify the impact of events
• Events can pass from 0 to 9 parameters by default, generate more at your needs
• Chronicled events (pre and post event)
• Event priority
• Nested event calls

Maven

<repository>
    <id>jitpack.io</id>
    <url>https://jitpack.io</url>
</repository>

<dependency>
    <groupId>com.github.Stephcraft.Events</groupId>
    <artifactId>v2</artifactId>
    <version>main-SNAPSHOT</version>
    <scope>provided</scope>
</dependency>

V1

Demo | Post

Features

• Interfaceless implementation of events utilizing reflection
• trigger(...)
• bind(reference, methodName) / unbind(reference, methodName)
• bound(reference, methodName)

Maven

<repository>
    <id>jitpack.io</id>
    <url>https://jitpack.io</url>
</repository>

<dependency>
    <groupId>com.github.Stephcraft.Events</groupId>
    <artifactId>v1</artifactId>
    <version>main-SNAPSHOT</version>
    <scope>provided</scope>
</dependency>

Some code

class Player {
    
    // Player emits this event
    public final Event.P3<Boolean, Variable<Integer>, Variable<Item>> onCollect;
    
    // this event may be cancellable and be boundable to before and after it occurs
    public Player() {
        onCollect = Event.P3.create(CANCELLABLE, CHRONICLED)
    }
    
    // when item is collected
    public void handleItemCollection() {
        onCollect.trigger(
        
            // event parameters
            naturalPickup, Variable.of(xp), Variable.of(item),
            
            // event action
            (naturalPickup, xp, item) -> {
                // handle item collection (if not cancelled)
            }
        )
    }
}

class Droid {
    
    // Droid listens to player's event
    public final Listener.P3<Boolean, Variable<Integer>, Variable<Item>> onPlayerCollect = this::onPlayerCollect;
    public final Listener.P3<Boolean, Constant<Integer>, Constant<Item>> onPlayerCollected = this::onPlayerCollected;
    
    // when multiple listeners are present for the same event you may also specify priority and ignore cancelled
    public Droid() {
        player.onCollect.bind(PRE, onPlayerCollect);
        player.onCollect.bind(POST, onPlayerCollected);
    }
    
    // before event occurs
    public void onPlayerCollect(Boolean naturalPickup, Variable<Integer> xp, Variable<Item> item) {
        item.set(Items.DIRT.get());
        System.out.println("Player is collecting dirt");
    }
    
    // after event occured (parameters are immutable)
    public void onPlayerCollected(Boolean naturalPickup, Constant<Integer> xp, Constant<Item> item) {
        System.out.println("Player collected " + item.getName());
    }
}