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/

Othman Benchekroun · Accepted Answer · 2017-05-08 07:56:25Z

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

Thanks @BadrBellaj, that question didn't appear with the similar questions — Othman Benchekroun
– Othman Benchekroun, Commented May 8, 2017 at 20:49

JohnAllen · Accepted Answer · 2017-09-11 06:50:52Z

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()

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