I am trying to implement an await
function which local variable I am trying to access outside the function. However, I'm not getting the value which is defined inside function.
async CreateProduceRateAsset(data, callback) {
// Create a new file system based wallet for managing identities.
try {
var TimeStamp = new Date();
var TxId = '';
var blockNumber = '';
const result = await contract.submitTransaction('CreateProduceRateAsset', args);
await network.addBlockListener('block-listener', (err, block) => {
if (err) {
console.log(err);
return;
}
TimeStamp = block.data.data[0].payload.header.channel_header.timestamp;
var Tx_id = block.data.data[0].payload.header.channel_header.tx_id;
var BlockNO = block.header.number;
console.log('TxId', Tx_id)
console.log('blockNumber', BlockNO)
TxId = Tx_id
blockNumber = BlockNO
return TimeStamp, Tx_id, BlockNO
});
console.log('Timestamp', TimeStamp)
console.log('TxId 123', TxId)
console.log('blockNumber 123', blockNumber)
response.data = result
return callback(response);
} catch (error) {
response.httpstatus = 404;
response.message = `Failed to get MVP Price ${error.message} `;
return callback(response);
}
};
In the above code, I want to access Tx_id
, Timestamp
and BlockNO
. For that, I am assigning a local variable to a global variable, however, I'm still getting the value of those as blank.
Could someone help me to get those values?
You have to put your return into a variable like this:
var data = await network.addBlockListener('block-listener', (err, block) => {
if (err) {
console.log(err);
return;
}
TimeStamp = block.data.data[0].payload.header.channel_header.timestamp;
var Tx_id = block.data.data[0].payload.header.channel_header.tx_id;
var BlockNO = block.header.number;
console.log('###########TxId#####################', Tx_id)
console.log('###########blockNumber#####################', BlockNO)
TxId = Tx_id
blockNumber = BlockNO
return {TimeStamp, Tx_id, BlockNO};
});
console.log('*************** Timestamp:: **********************', data.TimeStamp)
console.log('###########TxId#####################123', data.Tx_id)
console.log('###########blockNumber#####################123', data.BlockNO)
Now you can store all your values into data
and put them into the desired variables.
if I understand network.addBlockListener
is a callback-based API and not return a promise so you cant await
it, I guessed that you use https://hyperledger.github.io/fabric-sdk-node/release-1.4/module-fabric-network.Network.html
Here is your code with my comments
async CreateProduceRateAsset(data, callback) {
// Create a new file system based wallet for managing identities.
try {
var TimeStamp = new Date();
var TxId = '';
var blockNumber = '';
const result = await contract.submitTransaction('CreateProduceRateAsset', args);
// --> this api is callback based and wont not return a promise so you cant await it
await network.addBlockListener('block-listener', (err, block) => {
if (err) {
console.log(err);
return;
}
TimeStamp = block.data.data[0].payload.header.channel_header.timestamp;
// --> becasue you are inside a function these vars are not the same as the one ouside the call back , becasue they are scoped to this function
var Tx_id = block.data.data[0].payload.header.channel_header.tx_id;
var BlockNO = block.header.number;
console.log('###########TxId#####################', Tx_id)
console.log('###########blockNumber#####################', BlockNO)
TxId = Tx_id
blockNumber = BlockNO
// --> you can only return one value in js, also this reurn is useless since you dont call this callback
// --> better way to get these vars outside the callback is to pass them to your own callbak like this `callback(response,TimeStamp, Tx_id, BlockNO)`
return TimeStamp, Tx_id, BlockNO
});
console.log('*************** Timestamp:: **********************', TimeStamp)
console.log('###########TxId#####################123', TxId)
console.log('###########blockNumber#####################123', blockNumber)
response.data = result
return callback(response);
} catch (error) {
// if(error) throw error;
// response.error = error;
response.httpstatus = 404;
response.message = `Failed to get MVP Price ${error.message} `;
return callback(response);
}
};
if you need to use async/await with network.addBlockListener
you can use utils.promisify
to convert it to promise-based API but I don't recommend it since this an event listener
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