HelloWorld contract using truffle v3.2.1

Question

I made my first very simple HelloWorld smart contract :

pragma solidity ^0.4.4;

contract HelloWorld {
    uint public balance;

    function sayHi() returns (bool success) {
        balance = 1000;
        return true;
    }
}

Trying to deploy all using truffle in a testrpc local network My deploy contracts looks like this :

var HelloWorld = artifacts.require("./HelloWorld.sol");
module.exports = function(deployer) {

  deployer.deploy(HelloWorld);
};

I truffle build && truffle migrate and then try to use my contract, I can see that my contract is correctly deployed, I can access my testrpc network (accounts available etc ...) but I try to get my balance :

truffle(development)> var aHelloWorld = HelloWorld.deployed()
undefined
truffle(development)> aHelloWorld.balance.call().then(console.log)
TypeError: Cannot read property 'call' of undefined

It doesn't find my balance property ... however if I console.log my aHelloWorld object, I can see that it has a balance property.

and then I called :

truffle(development)> aHelloWorld.toString()
'[object Promise]'

So it seems that my contract stays as a promise, I tried :

truffle(development)> aHelloWorld.then(function (myContract) { 
  myContract.sayHi().then(); 
  console.log(myContract.balance.call().then(console.log))
})
Promise { <pending> }
undefined
truffle(development)> { [String: '1000'] s: 1, e: 3, c: [ 1000 ] }

It correctly changed my balance, I am happy but reaally confused... I've watched few tutorials and also read some answers here about basic steps like Truffle error: Cannot read property 'call' of undefined It works for them all by doing HelloWorld.deployed().balance.call()...

I mean accessing the contract directly through HelloWorld.deployed() without waiting for the promise ... Is it because the version of truffle I use or am I doing something wrong ?

UPDATE : Even truffle tutorial shows direct access to the deployed() object : http://truffle.readthedocs.io/en/latest/getting_started/testing/

score 2 · Answer 1 · answered May 08 '17 at 07:56

2

Can't believe I found answer on a youtube video comment :

Truffle change to call this way

HelloWorld.deployed().then(a => console.log(a.address))

link to the youtube video : link

Which mean in my case HelloWorld.deployed().then(a => console.log(a.balance)), or HelloWorld.deployed().then(a => console.log(a.balance.then(console.log))), to get answer directly So yes truffle changed their way of accessing contract in newer versions, they should update their doc

answered May 08 '17 at 07:56

Othman Benchekroun

215
2
8

1

https://ethereum.stackexchange.com/questions/11935/problem-with-truffle-console-cannot-read-property-call-of-undefined/13541#13541 – Badr Bellaj May 08 '17 at 10:25
Thanks @BadrBellaj, that question didn't appear with the similar questions – Othman Benchekroun May 08 '17 at 20:49

score 1 · Answer 2 · edited Sep 11 '17 at 06:50

In order to make life a little bit easier you can also do it like this:

First you can assign the contract to variable:

truffle(development)> HelloWorld.deployed().then(function(instance){helloWorld=instance})

Since balance is a public variable the compiler will create a getter function for you. To get the balance you can call:

truffle(development)> helloWorld.balance.call()

or to assign the balance to a variable you can call:

truffle(development)> var balance = helloWorld.balance.call()

To call the function sayHi you would call:

truffle(development)> helloWorld.balance.sayHi()

HelloWorld contract using truffle v3.2.1

2 Answers2