Add operation to create a book review

Now that we have two entities in our model, we need to add a mechanism for creating a new entry for a book review. To achieve this, we will define an operation to create a new book review.

Open the file src/main/operations.rell and add the following Rell code:

src/main/operations.rell

operation create_book_review(isbn: text, reviewer_name: text, review: text, rating: integer) {
  val book = book @ { .isbn ==  isbn };
  create book_review (
    book,
    reviewer_name,
    review,
    rating
  );
}

This operation is similar to the create_book operation, but for this operation, we need to establish a connection between the review and the book. In our example, the key for a book is the isbn, so we will use this to associate the review with a specific book.

Inside the operation

We're sending the operation to create a book review to a Chromia node, which will generate a new transaction and persist the data in the dapp table state, as illustrated below.

• A user signs the transaction create_book_review("ISBN1234", "Alice", "It was a great book!", 5).
• The transaction is sent to the Chromia Node, where it undergoes validation and is subsequently forwarded to the blockchain.
• Inside the operation:

  val book = book @ { .isbn ==  isbn };
  create book_review (
    book,
    reviewer_name,
    review,
    rating
  );

The book is queried from the dapp table state, and then a new row is created for the book_review with a relationship to the book.

• If the transaction is confirmed, it is added to a block on the blockchain, and the dapp table state is updated accordingly.

Add unit tests

Let's incorporate another test to ensure our book review operations function as expected. In Rell, we can use test modules to create our tests, which is relatively straightforward.

Open the src/test/book_review_test.rell file and update the imports to include book_review and create_book_review:

src/test/book_review_test.rell

import main.{ book, create_book, get_all_books, book_review, create_book_review };

After updating the imports, add the following test code to the same file:

src/test/book_review_test.rell

function test_add_book_review() {
    rell.test.tx()
        .op(create_book("123", "Book1", "Author1"))
        .op(create_book_review("123", "Reviewer1", "ReviewText1", 5))
        .op(create_book_review("123", "Reviewer2", "ReviewText2", 3))
        .run();

    val reviews = book_review @* { };
    val book = book @ { .isbn == "123" };

    assert_equals(reviews.size(), 2);
    assert_equals(book, reviews[0].book);
    assert_equals(reviews[0].reviewer_name, "Reviewer1");
    assert_equals(reviews[0].review, "ReviewText1");
    assert_equals(reviews[0].rating, 5);
}

This code executes a transaction with three operations. First, we create a book, then two reviews, and connect them to the book we created.

• assert_equals(reviews.size(), 2); checks that we have two entries.
• assert_equals(book, reviews[0].book); ensures that the correct book is connected to the review.
• assert_equals(reviews[0].reviewer_name, "Reviewer1") confirms the reviewer's name.
• assert_equals(reviews[0].review, "ReviewText1") checks the review text.
• assert_equals(reviews[0].rating, 5) verifies the rating.

After setting up the tests, we can run them:

chr test

After running the test, you should see the test results indicating that all tests have passed:

TEST RESULTS:

OK test.book_review_test:test_add_book
OK test.book_review_test:test_get_books
OK test.book_review_test:test_add_book_review

SUMMARY: 0 FAILED / 3 PASSED / 3 TOTAL

***** OK *****

Test it with a local Chromia node

To validate our newly created operation on a local Chromia node, follow these steps:

1. Update or start the local Chromia node:

   • If the node is already running, use the following command to update it:

     chr node update

   • If the node is not already running, start it with:

     chr node start

   Note: After running chr node update, it might take a moment for the update to be reflected. You may need to wait for the next block to be processed before the query becomes available.

2. Create a transaction to add a book review:

   chr tx --await create_book_review "ISBN1234" "Alice" "It was a great book" 5

   The expected result should be:

   transaction with rid TxRid(rid=<RID>) was posted CONFIRMED

This confirms that the transaction was added to the blockchain, and the state now contains a row with the book review data.