先前使用 Query 物件是在 in-memory的HashMap 所以更新就更新了，這次接surrealDB試試要透過Surreal的API(SQL)存取

流程大約是cqrs套件裡收到command後，如果執行成功會套用到aggregate並透過query派送至各下游view
cqrs.execute(command)
--> store.load(aggregate)
--> handle(command)
--> apply(aggregate)
--> store.commit(events)
--> query.dispatch(events)
--> view.update

先建立BookDto：

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BookDto {
    pub book_id: String,
    pub title: String,
    pub isbn10: String,
    pub description: String,
    pub copies: u32,
    pub available_copies: u32,
}

加BookQuery物件

#[derive(Debug, Clone)]
pub struct BookQuery {
    pub db: Surreal<Db>,
}

impl BookQuery {
    pub async fn insert_book(&self, book_dto: &BookDto) {
        let result: Content<'_, Db, &BookDto, Vec<BookDto>> = self.db
            .create("books")
            .content(book_dto);
        let _ = result.await.ok();
    }
    pub async fn ingest_book(&self, copies: u32, id: String) {
        let ql = format!("UPDATE books SET copies = copies + {} \
                    , available_copies = available_copies + {} \
                     where book_id = '{}';", copies, copies, id);
        let _ = self.db
            .query(ql)
            .await.ok();
    }
    pub async fn lent_book(&self, id: String) {
        let ql = format!("UPDATE books SET available_copies = available_copies - 1 \
                     where book_id = '{}';", id);
        let _ = self.db
            .query(ql).await
            .ok();
    }
    pub async fn returned_book(&self, id:String) {
        let ql = format!("UPDATE books SET available_copies = available_copies + 1 \
                     where book_id = '{}';", id);
        let _ = self.db
            .query(ql).await
            .ok();
    }
}

套Query trait

#[async_trait]
impl Query<Book> for BookQuery {
    async fn dispatch(&self, aggregate_id: &str, events: &[EventEnvelope<Book>]) {
        for event in events {
            match &event.payload {
                BookEvent::BookCreated { id, title, isbn10, description } => {
                    let book_dto = BookDto {
                        book_id: id.to_string(),
                        title: title.to_string(),
                        isbn10: isbn10.to_string(),
                        description: description.to_string(),
                        copies: 0,
                        available_copies: 0,
                    };
                    self.insert_book(&book_dto).await;
                }
                BookEvent::BookIngested { id, copies } => {
                    self.ingest_book(*copies, id.to_string()).await;
                }
                BookEvent::BookLent(record) => {
                    self.lent_book(aggregate_id.to_string()).await;
                }
                BookEvent::BookReturned(record) => {
                    self.returned_book(aggregate_id.to_string()).await;
                }
            }
        }
    }
}

在main補上註冊：

let book_query = BookQuery { db: db.clone() };
let book_cqrs = CqrsFramework::new(
    book_store,
    vec![Box::new(book_query)], 
    book_service.clone());

測試：

建檔入庫後

======== Books ========
[
    BookDto {
        book_id: "test-book-1",
        title: "Rust 語言開發實戰",
        isbn10: "1234567890",
        description: "使用rust，併同cqrs框架，實現event sourcing",
        copies: 2,
        available_copies: 2,
    },
]

一借閱

======== Books ========
[
    BookDto {
        book_id: "test-book-1",
        title: "Rust 語言開發實戰",
        isbn10: "1234567890",
        description: "使用rust，併同cqrs框架，實現event sourcing",
        copies: 2,
        available_copies: 1,
    },
]

二借閱

======== Books ========
[
    BookDto {
        book_id: "test-book-1",
        title: "Rust 語言開發實戰",
        isbn10: "1234567890",
        description: "使用rust，併同cqrs框架，實現event sourcing",
        copies: 2,
        available_copies: 0,
    },
]

一還

======== Books ========
[
    BookDto {
        book_id: "test-book-1",
        title: "Rust 語言開發實戰",
        isbn10: "1234567890",
        description: "使用rust，併同cqrs框架，實現event sourcing",
        copies: 2,
        available_copies: 1,
    },
]

書籍的View (Query端)會隨著事件的推移進行更新，後面再處理reader vs book 的query