Deploying smart contract programatically from web3 / nodejs

Question

I'm building a Dapp where, whenever a user creates an account, it automatically creates an Ethereum address for the user (I'm exposing the personal module over RPC for now, but it's just for playing purposes). I now want to automatically deploy a contract when a user creates an account, ideally to make that user the only address capable of interacting with that contract.

Following some tutorials (this), I installed solc and changed my code to

var Web3 = require('web3');
var web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
const solc = require('solc');
var fs = require('fs');
const input = fs.readFileSync('contracts/helloWorld.sol');
const output = solc.compile(input.toString(), 1);
const bytecode = output.contracts['helloWorld'].bytecode;
const abi = JSON.parse(output.contracts[':helloWorld'].interface);

This however, throws an error TypeError: Cannot read property ':helloWorld' of undefined. After some investigation, I realised the output is returning { errors: [ ':1:1: Error: Expected import directive or contract definition.\npragma solidity ^0.4.11;\n^\n' ] }

Finally, even after seeing this answer, I still can't figure out why. I paste my contract code on Remix IDE and it does not throw any error.

My contract code (the test one I'm using now) is

pragma solidity ^0.4.11;

contract helloWorld {
    /* Constructor */
    address owner;

    function helloWorld() {
        owner = msg.sender;    
    }

    function remove() {
        if (msg.sender == owner) {
            // Suicide and send funds to owner
            selfdestruct(owner);
        }
    }

    function greet() constant returns (bytes32, address) {
        if (msg.sender == owner) {
            bytes32 hello = "hello";
            return (hello, msg.sender);
        }
    }

}

Any help would be much appreciated, been stuck for a while :)

Answer 1

Try just cutting and pasting your code into the nodejs terminal (note the grave ticks) so...

var source = `pragma solidity ^0.4.11;

contract helloWorld {
    /* Constructor */
    address owner;

    function helloWorld() {
        owner = msg.sender;    
    }

    function remove() {
        if (msg.sender == owner) {
            // Suicide and send funds to owner
            selfdestruct(owner);
        }
    }

    function greet() constant returns (bytes32, address) {
        if (msg.sender == owner) {
            bytes32 hello = "hello";
            return (hello, msg.sender);
        }
    }

}`

var output = solc.compile(source);

The import stuff is all sorts of weird still for me too

Answer 2

I think it's an encoding issue. https://github.com/ethereum/solc-js/issues/90

Your error message comes from this line: \npragma solidity ^0.4.11;\n^\n'

When I ran it in my console, the toString resulted in \npragma solidity ^0.4.11;\n\n, so I think the \n^ literal is causing solc to mess up.

Answer 3

using solc version 0.4.19, Contract object can be accesible by adding : prefix to the contract name,

const output = solc.compile(input.toString(), 1); const bytecode = '0x' + output.contracts[':helloWorld'].bytecode; const abi = JSON.parse(output.contracts[':helloWorld'].interface);