How do i use .send() to fire methods of my smartcontract?

Question

I have looked alot for information about this and lastly i turn myself to here. I've written a smartcontract and deployed it to Ropsten . I am then using web3.js to interact with my smartcontract, i can use .call methods with no errors, but i have no idea how to fire methods that change the state, in this case mint, burn and send_X_tokens. From web3 docs it is stated in examples to be like this

myContract.methods.myMethod(123).send({from: 'ADDRESS'})
.then(console.log(receipt){
});

but that doesn't help me much. I assume i have to setup my account to be open or create and sign a transaction in order to use gas, but i cannot find anything on how to do that.

So thus far my code looks like this.

contract.methods.mint().send({ from: '0x76a9CEA17DbA8a371944d00a2E9A17AA3669B392', gas: 4000000 }).then(console.log(result))

And the error looks like this.

(node:28313) UnhandledPromiseRejectionWarning: Error: Returned error: The method eth_sendTransaction does not exist/is not available
    at Object.ErrorResponse (/home/ubuntu/ethereum_website/node_modules/web3-core-helpers/src/errors.js:29:16)
    at /home/ubuntu/ethereum_website/node_modules/web3-core-requestmanager/src/index.js:140:36
    at XMLHttpRequest.request.onreadystatechange (/home/ubuntu/ethereum_website/node_modules/web3-providers-http/src/index.js:96:13)
    at XMLHttpRequestEventTarget.dispatchEvent (/home/ubuntu/ethereum_website/node_modules/xhr2-cookies/dist/xml-http-request-event-target.js:34:22)
    at XMLHttpRequest._setReadyState (/home/ubuntu/ethereum_website/node_modules/xhr2-cookies/dist/xml-http-request.js:208:14)
    at XMLHttpRequest._onHttpResponseEnd (/home/ubuntu/ethereum_website/node_modules/xhr2-cookies/dist/xml-http-request.js:318:14)
    at IncomingMessage.<anonymous> (/home/ubuntu/ethereum_website/node_modules/xhr2-cookies/dist/xml-http-request.js:289:61)
    at emitNone (events.js:111:20)
    at IncomingMessage.emit (events.js:208:7)
    at endReadableNT (_stream_readable.js:1064:12)
    at _combinedTickCallback (internal/process/next_tick.js:138:11)
    at process._tickDomainCallback (internal/process/next_tick.js:218:9)

Help me solve this (probably) most basic puzzle.

Answer 1

The solution was to create and add the account from which to send the transaction into a wallet.

adding the line

web3.eth.accounts.wallet.add('address_private_key')

above the method.send() fixed it for me.

Answer 2

Have you defined mint function as accepting any arguments?

If so, I think you need to pass argument(s) like

myContract.methods.mint(mintAmount).send({ from: accounts[0] }) .on(“receipt”, receipt => console.log(receipt))

https://web3js.readthedocs.io/en/v1.2.0/web3-eth-contract.html#methods-mymethod-send

I hope your problem will be solved