用法

// 建立 DB
let db = Surreal::new::<Mem>(()).await?;
db.use_ns("test").use_db("test").await?;
let repo = SurrealEventRepository { db: db.clone() };

// 建立 reader cqrs，這次注入昨天寫好的Query
let reader_query = ReaderQuery { db: db.clone() };
let reader_service = ReaderService {};
let reader_store: PersistedEventStore<SurrealEventRepository, Reader>
    = PersistedEventStore::new_event_store(repo.clone());
let reader_cqrs = CqrsFramework::new(
    reader_store,
    vec![Box::new(reader_query)],
    reader_service);

執行以下建立讀者指令

let _ = reader_cqrs.execute("test-reader-1", ReaderCommand::CreateReader {
    name: "John Smith".to_string(),
}).await;
let _ = reader_cqrs.execute("test-reader-2", ReaderCommand::CreateReader {
    name: "Mary Ann".to_string(),
}).await;

查閱我們 CQRS 中 Query專用的資料表

let reader_dtos: Vec<ReaderDto> = repo.db
    .query("SELECT * FROM readers ORDER BY id")
    .await?
    .take(0)?;
println!("======== Readers ========\n{:#?}", reader_dtos);

======== Readers ========
[
    ReaderDto {
        reader_id: "test-reader-1",
        name: "John Smith",
        books_borrowed: 0,
        books_borrows: [],
        next_due_date: None,
    },
    ReaderDto {
        reader_id: "test-reader-2",
        name: "Mary Ann",
        books_borrowed: 0,
        books_borrows: [],
        next_due_date: None,
    },
]

借閱指令

let _ = reader_cqrs.execute("test-reader-1", ReaderCommand::BorrowBook {
    book_id: "test-book-1".to_string(),
    borrowed_date: Utc::now(),
    due_date: Utc::now().add(chrono::Duration::days(7)),
}).await;

Query資料表

======== Readers ========
[
    ReaderDto {
        reader_id: "test-reader-1",
        name: "John Smith",
        books_borrowed: 1,
        books_borrows: [
            ReaderBorrows {
                book_id: "test-book-1",
                book_name: "Rust 語言開發實戰",
                borrowed_date: 2023-10-05T04:50:06.196949500Z,
                due_date: 2023-10-12T04:50:06.196981600Z,
            },
        ],
        next_due_date: Some(
            2023-10-12T04:50:06.196981600Z,
        ),
    },
    ReaderDto {
        reader_id: "test-reader-2",
        name: "Mary Ann",
        books_borrowed: 0,
        books_borrows: [],
        next_due_date: None,
    },
]

對比前一次使用InMemory Store是用HashMap，reader無法參照book的aggregate，這回使用surrealDB我們在Query的dispatch裡呼叫讀取book的 title，就可以帶出書名。在此查詢就不需要去JOIN 書籍的資料表。

歸還書籍的操作

let _ = reader_cqrs.execute("test-reader-1", ReaderCommand::ReturnBook {
    book_id: "test-book-1".to_string(),
    return_date: Utc::now().add(chrono::Duration::days(2)),
}).await;

結果

======== Readers ========
[
    ReaderDto {
        reader_id: "test-reader-1",
        name: "John Smith",
        books_borrowed: 0,
        books_borrows: [],
        next_due_date: None,
    },
    ReaderDto {
        reader_id: "test-reader-2",
        name: "Mary Ann",
        books_borrowed: 0,
        books_borrows: [],
        next_due_date: None,
    },
]

正確顯示當下狀態