accessing truffle contract abstractions from external JS script

Question

When writing tests in truffle (v3.2.1) I can forget about things like a contract's ABI and address and just use ContractName.deployed() to interact with a contract on my testrpc chain. How can I mimic this behavior in my external Javascript code, that is, not by using truffle's built-in console or truffle test? Is there a library I need to import in my script or do I need to manually get the ABI and deployment address of the contract as if I was not using Truffle?

I'd be also fine if I could use those contract abstraction by running my JS code through truffle, but I'm not sure of how would I do that.

Thanks!

Answer 1

Not sure whether this is the intended way, but experimenting with bits and pieces of code found around the Internet resulted in something that seems to be working. Here's what I did in my javascript app:

....
const artifacts = require('../build/contracts/MyContract.json')
const contract = require('truffle-contract')
let MyContract = contract(artifacts);
MyContract.setProvider(web3.currentProvider);    
return MyContract.deployed().then(function(instance){      
  return instance.sendTransaction(param1, param2, {from: accounts[0]});
}).then(function(tx_id){
....

The json file is what was produced by truffle when migrating MyContract. Note that I had to install truffle-contract (on top of truffle) for this to work. If anyone has a more elegant way of doing this, please share!

Answer 2

Assuming I have a HelloWorld contract with a uint public balance variable and I'd want to get its balance I'd do the following:

let Web3 = require('web3')
var provider = new Web3.providers.HttpProvider("http://localhost:8545")
let contract = require('truffle-contract')
let HelloWorld = contract(require('./build/contracts/HelloWorld.json'))

HelloWorld.setProvider(provider);
HelloWorld.deployed().then(contract => {
   return contract.balance()
}).then(response => {
   console.log(response)
})

Worked for me! Let me know if this works for you!

Answer 3

If you where to input it manually you can use something like this in your js

var contractAddressED = 'HERE YOUR CONTRACT ADDRESS';

var byteCodeED = 'HEREYOUR BYTECODE IF YOU WANT TO';

var contractABIED = HEREYOURABI;

contractED = web3.eth.contract(contractABIED).at(contractAddressED);

To interact with your functions you can then do something like:

//to read a state variable eg. owner

contractED.owner(function(err, result) { // document.getElementById('name').innerHTML = 'Hello, ' + result; or jquery $("#owner").html('some text: ' + result); });

//to trigger a function

$("#clearstatus").click(function() { contractED.clearstatusjudging(function(err, result) { console.log(err, result); }) });

hope this helps!