I'm trying to implement factory contracts in Mix but can't get the child to create and return an address. I deploy Factory but when I try to call the creator function,


Mix throws:

JavaScript  error   14:18:06    web3.js - line 3881 - Uncaught invalid address

contract Gizmo
    int public value;
    function Gizmo(int v) {
        value = v;

contract Factory
    address gizmoAddr;
    function Create(int _value) returns (address) {
        gizmoAddr = new Gizmo(_value);
        return gizmoAddr;

1 Answer 1


You need to specify an address that you are sending the transaction from

contracts['Factory'].contract.Create(10,{from: web3.eth.accounts[0],gas:100000});

You can change the gas as needed, but 100,000 should be enough for this.

  • Thanks. How do I call the gizmo by address in js, e.g contracts[0x97fea572b69e27ca44475534359d9bb932133fb3].contract.value()?
    – o0ragman0o
    Commented May 16, 2016 at 5:52
  • You can't really return a value from an on-chain transaction, so the best way is probably to declare address constant gizmoAddr and then just use the ABI to create a new contract object in web3 Commented May 16, 2016 at 10:55
  • Or you can put a function into Factory that lets you call Gizmo without needing to manually use Gizmo's address Commented May 16, 2016 at 10:56
  • I'm not understanding this. I need factory to call the gizmo instance after it's created. I can't declare gizmoAddr as constant as it needs to be created dynamically. Also, to Factory, I added the function: function getGizmoVal() returns (int) { return gizmoAddr.val(); } but when I call it with JS responds with a different return value every time. :/
    – o0ragman0o
    Commented May 17, 2016 at 12:13
  • function getGizmoVal() constant returns (int) works correctly
    – o0ragman0o
    Commented May 17, 2016 at 13:08

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