Hyperledger Fabric Version 2: How to query Block Header such as data hash, previous hash by using Fabric Node SDK 2.2

Question

I am trying to build a decentralized app that able to do show the block header like data hash, the previous hash of the block when a user submits a new transaction. However, It seems like the new version of Fabric Node SDK 2.2 removes the function queryblock.

I refer on the documentation at https://hyperledger.github.io/fabric-sdk-node/release-2.2/module-fabric-network.html and currently still looking for some workaround to show the block info of the user's transaction.

The ideal output that I wish to achieved is almost similar to what Hyperledger Explorer provide.The reference can be check at:

• https://github.com/hyperledger/blockchain-explorer

which show the information such as Number of Blocks, Data Hash, Previous Hash and other Block Information regarding the hash.

Some information that I able to gather

1. There are some information like BlockEvent that have the name blockData in the interface BlockEvent . However, I can't seem to find it when npm install i fabric-network .

   • https://hyperledger.github.io/fabric-sdk-node/release-2.2/module-fabric-network.BlockEvent.html

2. Since the user can query and check their hash with the ledger, a key or hash need to be returned to the user upon transaction success. Is there any API function for this? So far, I able to found there are getTransactionId() in the class Transaction . But is this one that I need to use?

   • https://hyperledger.github.io/fabric-sdk-node/release-2.2/module-fabric-network.Transaction.html

StackOverflow reference that I had gone over:

All of the reference since to deal with the old version of node SDK which is version 1.4.

• Hyperledger Fabric: How to Query blocks using fabric NodeSDK
• HyperLedger Fabric Get Block Info - using node.js
• how to display current hash,previous hash using node js on view pages for hyperledger fabric
• How do you calculate the Block Hash for the Current Block in Hyperledger Fabric with javascript?
• How to get history of asset with block hash in hyperledger fabric using node sdk

Answer 1

You can query block number by call function GetBlockByNumber of qscc contract. Example:

const contract = network.getContract('qscc');
const resultByte = await contract.evaluateTransaction(
    'GetBlockByNumber',
    channelName,
    String(blockNum)
);
const resultJson = BlockDecoder.decode(resultByte);
logger.debug('queryBlock', resultJson);