ActorES

这是一个旨在更实用而不是“照本宣科”的事件溯源和 CQRS 抽象。它建立在轻量级 actor 框架 Riker 之上。
警告 目前它几乎是 alpha 质量，功能尚不完整，API 仍在变化。

如何使用

此库为 Riker 添加了一些额外的与事件溯源相关的概念，最显著的是 实体，它代表一个处理外部命令和业务逻辑的领域。使用 Riker 的常规机制（参见 创建 actor）通过 Entity actor 创建。

let entity = actor_system.actor_of_args::<Entity<MyEntity>, _>("my-entity", SomeArgs)`;

定义您的实体

假设 MyEntity 是一个用户提供的实现 ES 特质的 struct。

struct MyEntity;

#[async-trait]
impl ES for MyEntity {
  type Args = SomeArgs; // the arguments passed to the constructor
  type Model = MyData; // The "model" is the data that is to be persisted along with its changes.
  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<CQRS<Self::Cmd>>, _args: Self::Args) -> Self {
    MyEntity
  }
  
  async fn handle_command(&mut self, cmd: Self::Cmd) -> Result<Self> {
    // 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(Event::Create(MyData).into())
    // or to update an existing entity
    // Ok(Event::Change("some id".into(), MyDataUpdate).into())
  }
}

模型和重新加载数据

定义您的聚合（数据模型），它可以处理的更新以及如何应用它们。

struct MyData {
  some_id: String,
  some_field: String,
  other_field: Option<String>
}

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

impl Model for MyData {
  type Change = MyDataUpdate;
  
  fn id(&self) -> EntityId {
    self.some_id.into()
  }
  
  fn apply_change(&mut self, change: Self::Change) {
    match change {
      MyDataUpdate::TheChange(field, other) => {
        self.some_field = field;
        self.other_field = Some(other);
      },
      MyDataUpdate::LittleChange(field) => {
        self.some_field = field;
      },
    }
  }
}

分发命令和查询

RikerES 提供了一个实体管理器，当实体被 register 时，它会创建和管理您的实体。它提供了一个更简单的 API 来发送命令和查询到正确的实体。

let mgr = Manager::new(actor_system).register::<MyEntity, _>(SomeStore::new(), SomeArgs);

let id = mgr.command(MyEntityCommands::DoSomething).await;
let data = mgr.query::<MyEntity>(id).await.unwrap();

同时（在我找到使它更自动化的方法之前），您还必须为实体和命令实现 EntityName，以便能够将命令分发到正确的实体。

impl EntityName for MyEntity {
  const NAME: &'static str = "my-entity";
}
impl EntityName for MyEntityCommands {
  const NAME: &'static str = "my-entity";
}