Solidity & truffle: get elements from strings array

Question

i'm glad to follow this forum, it is very helpful. I'm using truffle to develop contracts and i just found that dynamic arrays are not yet suported, for that reason i was using string arrays with a fixed lenght and i found that the element with index 0 is not showing anything and last one says undefined. do you know ay reason of that?, do i have to get elements in a different way??

This is the function in solidity:

pragma solidity ^0.4.21;
pragma experimental ABIEncoderV2;

contract Example {
    function getStringArray() public returns (string[]) {
        string[] memory resultStr = new string;
        resultStr[0] = "355555555";
        resultStr[1] = "2";
        resultStr[2] = "8888";
        return resultStr;
    }
}

I also did a test with truffle like this:

in javascript i test getting elements one by one and i got this:

var ExampleCont = artifacts.require("Example");

contract('ExampleCont', async(accounts) => {
    before(async () => {
    ExampleContract = await ExampleCont.new();
    });
    it('Upload File', async () => {
        let stringArray = await ExampleContract.getStringArray.call();
        console.log("list size=" + stringArray.lenght+"0="
              + stringArray[0] + "1="+stringArray[0]+", 2=" + stringArray[1] + "3=" + stringArray[2]);
    }
}

list size=3, value 0= , 1=355555555, 2=2, 3=undefined

any idea about what's happening in this case?, how do i have work well with string arrays to get all elements?

Answer 1

I believe this is something not available in Solidity yet (having array of string). Because string in solidity is array of bytes, and now if you see the treatment of string[] becomes 2 d array bytes[][] and that's a limitation with Solidity as of now.

Answer 2

I used ABIEncoderv2 with solidity v0.5.0, and below code works perfectly.

function _getStringArray() public view returns (string[] memory) {
    string[] memory resultStr = new string[](3);
    resultStr[0] = "355555555";
    resultStr[1] = "2";
    resultStr[2] = "8888";
    return resultStr;
}

JavaScript starts here. I have used "web3 ^1.0.0-beta.36". I have tested in Kovan network, so use your kovan INFURA configuration to see it works. It's what can I do for now.

const ABI = [{"constant":true,"inputs":[],"name":"_getStringArray","outputs":[{"name":"","type":"string[]"}],"payable":false,"stateMutability":"view","type":"function"}];
const infuraUrl = "INFURAURL";
const infuraKey = "INFURAKEY";
const web3 = new Web3(infuraUrl+infuraKey)


ReactDOM.render(
  <div id ="test"></div>,
  document.getElementById('app')
);

module.hot.accept();

function integrateContract() {
  return new Promise(function (resolve, reject) {
      var contract = new web3.eth.Contract(ABI, "0x9fb7ba497a7572cc3234c5d0ae4dddc08d7bc1c0");
      resolve(contract);
  });
}

function getList(){
  integrateContract().then(instance => { 
    console.log({instance})
    instance.methods._getStringArray().call().then(res=> {
      document.getElementById("test").append(res)
    })

  });
}

getList()