benjamin-allen / pubsubhub-rs

A publish/subscribe system written in rust.

PubSubHub-rs

A library that implements a publish/subscribe system in rust, as a learning exercise.

Subscribers

This library provides a trait called Subscriber with a type parameter A. A type that implements Subscriber<A> provides a method called receive which is called by a pubsub system and passed a reference to an instance of A.

Here's an example subscriber implementation:

struct Food {
    amount: i32,
}

struct Dog {
    total_eaten: i32,
}
impl Subscriber<Food> for Dog {
    pub fn receive(&mut self, event: &Food) {
        self.total_eaten += amount;
    }
    as_any!()
}

When a Dog is subscribed to a pubsub, and a Food event is published, the receive method will be called.

PubSub

The library doesn't actually define a particular PubSub struct, but allows you to turn any struct into a pubsub system with a macro listing the types it should publish.

struct Food { amount: i32 }
struct Sleep { time: i32 }

#[publishes(Food, Sleep)]
struct PubSubHub {
    /* Any other struct fields you want in your pubsub system */
}

The macro will fill in new methods that can be used to publish and subscribe to the events supported by that struct. So, for example, you could use the PubSubHub to publish_Food or publish_Sleep:

let mut p = PubSubHub::new();
let d = Dog { } // Assume dog implements Subscriber<Food> and Subscriber<Sleep>

p.subscribe_Food(Box::new(d));
p.subscribe_Sleep(Box::new(d));

let f = Food { amount: 80 }
p.publish_Food(&f) // Will call the receive method for the Subscriber<Food> implementation on Dog