How to provide data for sendTransaction using web3.js 1.0

Question

I'm using web3.js 1.0. I want to use sendTransaction method to call a contract method, but I don't know how to provide data parameter for it. For example suppose we have a contract named myContract and the method setValue in it, then we want to call the method with two parameters: 123 as uint and 'ABC' as string. so we have:

nodeUrl='...';
abi=...;
contractAddress='0x...';
web3 = new Web3(new Web3.providers.HttpProvider(nodeUrl));
myContract = new web3.eth.Contract(abi,contractAddress);
web3.eth.sendTransaction({
    from: '0x...',
    data: data
}, function(error, hash){
    ...
});

And we want to use the method as follows:

setValue(123,'ABC');

How can we set the data value for sendTransaction method?

P.S: I don't want to use Metamask. I am using my account directly in my javascript code.

Answer 1

Try this:

data: myContract.methods.setValue(123,'ABC').encodeABI()

BTW, you'll first need to unlock on your node the account that you specify in the from field (otherwise, you'll need to use web3.eth.sendSignedTransaction instead).

Answer 2

No need to set the data manually. You can use the web3 contract methods function. In your case, you can call the setValue(123,'ABC') like this:

myContract = new web3.eth.Contract(abi,contractAddress);
myContract.methods.setValue(123,'ABC')
.send({
     from: youraccount.address,
     to: myContract.options.address,
     value: 0, // Don't send ETH, this is a contract transaction
})

See the web3 docs for more information.

Keep in mind that this is not a "call". Your function changes the state of the smart contract. You can use methods.myMethod.call for executing EVM functions that do not create a transaction.

P.S: I don't want to use Metamask. I am using my account directly in my javascript code.