I have problem with smart contract development using Remix solidity in private blockchain by Geth. I have two smart contracts such as Factory contract and Contract contract.

I create the Factory contract and then I call the createContract and getContract function, it works normally but when i call the getNum function I can not get the number.

I run this code in Remix solidity by JavaScript VM and Test network by Ganache or TestRPC work fine but when i use it with Private blockchain using Geth it has this problem

Here is my code.

contract Factory {
  address[] newContracts;

  function createContract(uint num) {
    address newContract = new Contract(num);

  function getContract() view public returns(address[]) {
    return newContracts;

  function getNum(address _add) view public returns(uint) {
    return Contract(_add).getNum();

contract Contract {
  uint public Num;

  function Contract(uint num) {
    Num = num;

  function getNum() public returns(uint) {
    return Num;

the picture of smartcontract problem

1 Answer 1


In Contract add view-modifier to getNum

function getNum() public view returns(uint) {
    return Num;

Your calls worked in ganache/testrpc/remix because the test EVM is synchronous in nature. I.e., you'll be able to get return values of transactions, since sendTransaction calls are executed instantly.

enter image description here

  • 1
    I add view modifier to getNum in Contract but it still work the same problem !
    – yoyo
    Apr 25, 2018 at 5:13
  • 1
    yes ! I put the address with double-quotes.
    – yoyo
    Apr 25, 2018 at 5:35
  • I used the remix solidity with private blockchain using Geth not with JavaScript VM
    – yoyo
    Apr 25, 2018 at 5:44
  • Sorry.. Safari reseted my connection to JavaScript VM due to http/https. Anyway, it works with Web3 Provider and geth node with Clique PoA. Everything is fine (see updated screenshot).
    – ivicaa
    Apr 25, 2018 at 6:13
  • 1
    I think maybe I have problem to setup private blockchain by Geth. so do you know which way to setup private blockchain by Geth correctly.
    – yoyo
    Apr 25, 2018 at 8:44

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