RikerES

An event sourcing and CQRS astraction that aims to be practical more than "go by the book". It's built on top of Riker a lightweight actor framework.
WARNING It's pretty much alpha quality at the moment, features are still missing and the API is still changing.

How to use

This library adds a few extra event-sourcing related concepts to Riker, entities represent a domain and are the entry point where external commands and bussiness logic is handled. Created with the Entity actor using the usual Riker machinery(see creating actors). rust let entity = actor_system.actor_of_args::<Entity<MyEntity>, _>("my-entity", SomeArgs)`;

Defining your entity

MyEntity is a user supplied struct that implements the ES trait. ```rust struct MyEntity;

[async-trait]

impl ES for MyEntity { type Args = SomeArgs; // the arguments passed to the constructor type Agg = MyData; // The "aggregate" is the data that is to be persisted along with its updates. type Cmd = MyEntityCommands; // The external command or commands(often in the form of an enum) this entity can handle. // type Event = (); // TODO: Similar to commands but for handling events emitted by other entities. type Error = MyEntityError; // Error produced by the handler functions.

// Used to construct an entity, receives the Entity actor's context // to be able to create other actors and hold their references fn new(_cx: &Context>, _args: Self::Args) -> Self { MyEntity }

async fn handle_command( &mut self, cmd: Self::Cmd, ) -> Result>, Self::Error> { // do your command handling here and return a commit that will be persited // to the configured store(a simple memory store atm).

// when entities are created for the first time
Ok(Some(Event::Create(MyData).into()))
// or to update an existing entity
// Ok(Some(Event::Update("some id".into(), MyDataUpdate).into()))

} } ```

Aggregates and rehidrating an entity's state

Define your aggregate(the data model), the updates it can handle and how to apply them.

```rust struct MyData { someid: String, somefield: String, other_field: Option }

enum MyDataUpdate { TheChange(String, String), LittleChange(String), }

impl Aggregate for MyData { type Update = MyDataUpdate;

fn id(&self) -> EntityId { self.some_id.into() }

fn applyupdate(&mut self, update: Self::Update) { match update { MyDataUpdate::TheChange(field, other) => { self.somefield = field; self.otherfield = Some(other); }, MyDataUpdate::LittleChange(field) => { self.somefield = field; }, } } } Later the state of an entity can be queried with the entity actor. rust let mydata: MyData = ask(&actorsystem, &entity, Query::One("123".into())).await; ```