I am trying out a very simple contract on the Rinkeby testnet. Pretty much as simple as it gets:

pragma solidity ^0.4.17;

contract Root {
    string rootHash;

    function set(string x) public {
        rootHash = x;

    function get() public constant returns (string x) {
        return rootHash;


It stores an ipfs multihash, and allows retrieving it.

The write part seems to work, using this code: https://gist.github.com/pwrstudio/6c95043ae3bb6a9aef9734a3fc8469e7

I can see that the multihash is sent to the contract, encoded as hex: https://rinkeby.etherscan.io/tx/0x4d7b98cf577d580168d24b1f61bcbc60f3f919c751624793e83dd10191ebba98

But when calling the get function I get this error:

ERROR: The returned value is not a convertible string

Relevant js code:

return new Promise((resolve, reject) => {
  const rootContract = new web3.eth.Contract(abi, CONTRACT_ADDRESS)
    .then(res => console.log(res))
    .catch(e => console.log(e))

Any pointers on what I am doing wrong much appreciated!


There is a small typo in the definition of function get. You should define only the return type string in the function definition, but no variable name (x). This should make it work:

function get() public constant returns (string) {
    return rootHash;
  • 1
    Thanks a lot! That did it. (Turned out I had also specified to low gas limit for the set function call, causing it to fail, but with those two problems fixed, everything works.) – Rasmus Svensson Dec 5 '17 at 14:21

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