私が解決する必要がある問題は、いくつかのフィールド(address、book、num_of_days、borrower_addr、blk_data)を含む契約を保存することです。blk_dataはトランザクションリスト(ブロック番号とトランザクションアドレス)です。この質問と回答が役に立ちました。以下のように私のコードを共有したいと思います。お役に立てれば。
  
  - スキーマ定義。blk_dataを参照してください。
var ContractSchema = new Schema(
    {
        address: {type: String, required: true, max: 100},  //contract address
        // book_id: {type: String, required: true, max: 100},  //book id in the book collection
        book: { type: Schema.ObjectId, ref: 'clc_books', required: true }, // Reference to the associated book.
        num_of_days: {type: Number, required: true, min: 1},
        borrower_addr: {type: String, required: true, max: 100},
        // status: {type: String, enum: ['available', 'Created', 'Locked', 'Inactive'], default:'Created'},
        blk_data: [{
            tx_addr: {type: String, max: 100}, // to do: change to a list
            block_number: {type: String, max: 100}, // to do: change to a list
        }]
    }
);
  
  - MongoDBでコレクションのレコードを作成します。blk_dataを参照してください。
// Post submit a smart contract proposal to borrowing a specific book.
exports.ctr_contract_propose_post = [
    // Validate fields
    body('book_id', 'book_id must not be empty.').isLength({ min: 1 }).trim(),
    body('req_addr', 'req_addr must not be empty.').isLength({ min: 1 }).trim(),
    body('new_contract_addr', 'contract_addr must not be empty.').isLength({ min: 1 }).trim(),
    body('tx_addr', 'tx_addr must not be empty.').isLength({ min: 1 }).trim(),
    body('block_number', 'block_number must not be empty.').isLength({ min: 1 }).trim(),
    body('num_of_days', 'num_of_days must not be empty.').isLength({ min: 1 }).trim(),
    // Sanitize fields.
    sanitizeBody('*').escape(),
    // Process request after validation and sanitization.
    (req, res, next) => {
        // Extract the validation errors from a request.
        const errors = validationResult(req);
        if (!errors.isEmpty()) {
            // There are errors. Render form again with sanitized values/error messages.
            res.status(400).send({ errors: errors.array() });
            return;
        }
        // Create a Book object with escaped/trimmed data and old id.
        var book_fields =
            {
                _id: req.body.book_id, // This is required, or a new ID will be assigned!
                cur_contract: req.body.new_contract_addr,
                status: 'await_approval'
            };
        async.parallel({
            //call the function get book model
            books: function(callback) {
                Book.findByIdAndUpdate(req.body.book_id, book_fields, {}).exec(callback);
            },
        }, function(error, results) {
            if (error) {
                res.status(400).send({ errors: errors.array() });
                return;
            }
            if (results.books.isNew) {
                // res.render('pg_error', {
                //     title: 'Proposing a smart contract to borrow the book',
                //     c: errors.array()
                // });
                res.status(400).send({ errors: errors.array() });
                return;
            }
            var contract = new Contract(
                {
                    address: req.body.new_contract_addr,
                    book: req.body.book_id,
                    num_of_days: req.body.num_of_days,
                    borrower_addr: req.body.req_addr
                });
            var blk_data = {
                    tx_addr: req.body.tx_addr,
                    block_number: req.body.block_number
                };
            contract.blk_data.push(blk_data);
            // Data from form is valid. Save book.
            contract.save(function (err) {
                if (err) { return next(err); }
                // Successful - redirect to new book record.
                resObj = {
                    "res": contract.url
                };
                res.status(200).send(JSON.stringify(resObj));
                // res.redirect();
            });
        });
    },
];
  
  - レコードを更新します。blk_dataを参照してください。
// Post lender accept borrow proposal.
exports.ctr_contract_propose_accept_post = [
    // Validate fields
    body('book_id', 'book_id must not be empty.').isLength({ min: 1 }).trim(),
    body('contract_id', 'book_id must not be empty.').isLength({ min: 1 }).trim(),
    body('tx_addr', 'tx_addr must not be empty.').isLength({ min: 1 }).trim(),
    body('block_number', 'block_number must not be empty.').isLength({ min: 1 }).trim(),
    // Sanitize fields.
    sanitizeBody('*').escape(),
    // Process request after validation and sanitization.
    (req, res, next) => {
        // Extract the validation errors from a request.
        const errors = validationResult(req);
        if (!errors.isEmpty()) {
            // There are errors. Render form again with sanitized values/error messages.
            res.status(400).send({ errors: errors.array() });
            return;
        }
        // Create a Book object with escaped/trimmed data
        var book_fields =
            {
                _id: req.body.book_id, // This is required, or a new ID will be assigned!
                status: 'on_loan'
            };
        // Create a contract object with escaped/trimmed data
        var contract_fields = {
            $push: {
                blk_data: {
                    tx_addr: req.body.tx_addr,
                    block_number: req.body.block_number
                }
            }
        };
        async.parallel({
            //call the function get book model
            book: function(callback) {
                Book.findByIdAndUpdate(req.body.book_id, book_fields, {}).exec(callback);
            },
            contract: function(callback) {
                Contract.findByIdAndUpdate(req.body.contract_id, contract_fields, {}).exec(callback);
            },
        }, function(error, results) {
            if (error) {
                res.status(400).send({ errors: errors.array() });
                return;
            }
            if ((results.book.isNew) || (results.contract.isNew)) {
                res.status(400).send({ errors: errors.array() });
                return;
            }
            var resObj = {
                "res": results.contract.url
            };
            res.status(200).send(JSON.stringify(resObj));
        });
    },
];
               
              
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